DataGridView (dgr)

DataGrid (dgr) - Allows the user to display (and edit) a table of information.

1) What is the System.Windows.Forms.DataGrid control ?
This was the original control added in .NET 1.1.
In .NET 2.0 this was replaced with the DataGridView control.

2) How can I remove all the rows ?

objDataGridView.Rows.Clear 

3) How can I remove the gridlines ?
Set the CellBorderStyle to None

4) How can I always display the vertical scrollbar ?
By default the datagridview only displays scrollbars when they are needed.
If you do want scrollbars permanently displayed then you need to derive your own class.

5) How can I get the value in the first column ?
The first column is at cell position 0.

objDataGridViewRow.Cells(0).Value.ToString 

6) How can I display the scrollbars after its been disabled ?
If you set the Enabled property to False to disable a datagridview and then later change it back to True, the scrollbars are not displayed.
try repopulating the datagridview or don't disable this control

7) How can I maintain the scroll position ?

Me.dgrDataGrid.CurrentCell = 
Me.dgrDataGrid.FirstDisplayedScrollingIndex 

8) How can I display a string date column in a specific date format ?
You must use MMMM and not mmmm (lowercase)

Private Sub dgvDataGridView_CellFormatting(ByVal sender As Object, _ 
                                           ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) _ 
                                           Handles dgvProjects.CellFormatting 

   If Me.dgvDataGridView.Columns(e.ColumnIndex).Name = "DateStart" Then 
      If e.Value.ToString.Length > 0 Then 
         e.Value = CType(e.Value, System.DateTime).ToString("dd MMMM yy") 
      End If 
   End If 
End Sub 

9) How can I change the Row Height ?
Expand the Row Template for the default and change the height property to 16

10) How can I select the whole row ?
Change the SelectionMode property to FullRowSelect

11) How can I get the rowindex of the currently selected cell ?

Me.dgrDataGridView.CurrentRow.Index 

although this is no good if you are inside the SelectionChanged event, in this situation use the following line

Me.dgrDataGridView.SelectedRows.Item(0).Cells(0).RowIndex 

12) How can I select a different row ?

Me.dgrDataGridView.Rows(index).Selected = True 

13) How can I be notified when a different row is selected ?
Save a form-level variable to keep track of the last selected row.

Private ilastselectedrowindex As System.Int32 

Private Sub dgrDataGridView_CurrentCellChanged(---) 
   If (ilastselectedrowindex <> Me.dgrDataGridView.CurrentCell.RowIndex) Then 

   End If 
   ilastselectedrowindex = Me.dgrDataGridView.CurrentCell.RowIndex 
End Sub 

14) How can I check if a selection has been made ?

If (Me.dgrDataGridView.SelectedRows.Count > 0) Then 
End If 

15) How can I remove the current selection from the datagridview, so nothing appears selected ?

Me.dgrDataGridView.ClearSelection 

16) How can I enable typing a character and moving to that specific row (auto-complete for the first character) ?
It is possible to jump to the row starting with a particular letter.
This can be achieved using the KeyDown event.

17) How can I remove the currently selected rows from the datagridview ?

Dim irowno As Integer 
For irowno = dgrDataGridView.SelectedRows.Count - 1 To 0 Step -1 
   objDataRow = dgrDataGridView.SelectedRows(irowno) 
   dgrDataGridView.Rows.Remove(objDataRow) 

Next irowno 

18) How can I automatically scroll to the selected row ?

objDataGirdView.FirstDisplayedScrollingRowIndex 

19) How can I format a whole row ?
Have to do it cell by cell

Rows().Cells(0).Style.BackColor = 

20) How can I remove rows ?

dgvDataGridView.Rows.Clear(); 
dgvDataGridView.Rows.Remove(objDataGridViewRow) 

21) How can I shade the cells based on their value ?
This can be done using the CellFormatting event

22) How can I hide a column ?

dgvDataGridView.Columns(2).Visible = False 

23) How can I make the last column wide enough to occupy the rest of the grid ?
Set the AutoSizeMode for the last column to Fill
You should also set a MinimumSize

24) How can I prevent a column from being selected ?
This can be achieved by checking the column of the active cell in the CellBeginEdit event.

Private Sub dgrDataGridView_CellBeginEdit(---) 
   If (CType(sender, System.Windows.Forms.DataGridView).CurrentCell.ColumnIndex <> 1 Then 
      e.Cancel 
   End If 
End Sub 

25) How to sort a column that contains numbers
Make sure that the ValueType is set to a numeric data type

Me.dgrDataGrid.Columns(2).ValueType = System.Type.GetType("Double") 

26) How can I allow typing in a combo box cell ?
Two things have to be done.
The DropDownStyle property of the ComboBox editing control has to be changed to DropDown
Ensure that the entry made is added to the combobox collection.
The best place to add this entry is in the CellValidating event

Private Sub dgvDataGridView_CellValidating(ByVal sender As Object, _ 
                                           ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) _ 

   If Me.dgvDataGridView.Columns(e.ColumnIndex).Name = "ComboColumnName" Then 
      If Me.dgvDataGridView.Columns(e.ColumnIndex).Items.Contains(e.FormattedValue) = False Then 
         Me.dgvDataGridView.Columns(e.ColumnIndex).Items.Add(e.FormattedValue) 
      End If 
   End If 
End Sub 

27) How can I have a combobox display a subset based on the selection in another combobox column ?
To enable this you need two versions of the filtered list (or subcategory).
Once list has no filters and the other is filtered based on the selection in the first combobox.

Private Sub dgvDataGridView_CellBeginEdit(ByVal sender As Object, _ 
                                          ByVal e As System.Windows.Forms.DataGridViewCellCancelEventArgs) 

'set the combobox cell datasource to the filtered Binding Source
Dim objcomboboxcell As System.Windows.Forms.DataGridViewComboBoxCell 
   objcomboboxcell  = CType(Me.dgvDataGridView(e.ColumnIndex, e.RowIndex)   , _ 
                           System.Windows.Forms.DataGridViewComboBoxCell) 

   objcomboboxcell.DataSource = 

End Sub 

Private Sub dgvDataGridView_CellEndEdit(ByVal sender As Object, _ 
                                        ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) 

End Sub 

Properties

Methods

Events

Defining and Populating a DataGridView

Dim ascolumnsarray As String(,) 

'create the application DataSet
clsDataSet.mobjDataSet = New System.Data.DataSet() 

clsDataSet.mobjDataSet.Tables.Add(New System.Data.DataTable("Worksheets")) 

ascolumnsarray = DataGridWorksheets_DefineColumns() 
Call clsDataTable.DefineColumns(Me.dgrWorksheets, "Worksheets", ascolumnsarray) 

Call DataGridWorksheets_TablePopulate() 

Call clsDataGrid.ViewCreate(Me.dgrWorksheets, "Worksheets", True) 

Call clsDataGrid.TableStyleDefine("Worksheets", _ 
                                  Me.dgrWorksheets, _ 
                                  ascolumnsarray, _ 
                                  New clsDataGrid.DataGridFormatCellEventHandler(AddressOf DataGrid_CellFormatEvent), _ 
                                  System.Drawing.Color.DarkBlue, _ 
                                  System.Drawing.Color.White) 

ListView Equivalent

Properties to Change

DataGridViewColumn

The DataGridView control can have several different types of columns depending on what exactly you want to show.

You can access the columns in a DataGridView by using the Columns collection

dgvDataGridView.Columns 

You can access the selected columns by using the SelectedColumns collection

dgvDataGridView.SelectedColumns 

When data is not bound you should create an instance of a column type and then add it to the Columns collection.
When you define a column, you have to specify a cell template on which the column is based.

DataGridViewTextBoxColumn

This column type has a cell template defined for a textbox.
By default this column type has its cell template initialised to a new DataGridViewTextBoxCell.

Setting a Default Value

Inherit a class from DataGridViewColumn and override the DefaultNewRowValue property

Properties

DataGridViewComboBoxColumn

Used to display a drop-down list inside a column of cells.
You can populate the drop-down list either manually or by binding it to a data source through the DataSource, DisplayMember and ValueMember properties.

When you add rows to the datagridview make sure this column is assigned a value from the drop-down list.

Single Click on Drop-Down

It is possible to have the drop-down displayed on a single click rather than 2 clicks.

objDataGridView.EditMode = Windows.Forms.DataGridViewEditMode.EditOnEnter 

Display Drop-Down when you click on cell

objDataGridView_CellEnter() 
   If e.ColumnIndex = 2 Then 
      If Me.objDataGridView(e.ColumnIndex, e.RowIndex).EditType.ToString = _ 
         "System.Windows.Forms.DataGridViewComboBoxEditingControl" Then 
          System.Windows.Forms.SendKeys.Send("{F4}") 
      End If 
   End If 

Properties

Events

DataGridViewComboBoxColumn - Multiple Selection

CellFormatting

SelectionChanged

EditingControlShowing

m_objEditingComboBox = CType(e.Control, Forms.ComboBox) 

AddHandler m_objEditingComboBox.SelectedIndexChanged 
AddHandler m_objEditingComboBox.DropDown 
AddHandler m_objEditingComboBox.DropDownClosed 
AddHandler m_objEditingComboBox.KeyDown 
AddHandler m_objEditingComboBox.KeyUp 

Adding Columns

objdatagridviewcolumn = New System.Windows.Forms.DataGridViewColumn 
objdatagridviewcolumn.Name = "Title" 
objdatagridviewcolumn.Width = 100 
objdatagridviewcolumn.CellTemplate = New System.Windows.Forms.DataGridViewTextBoxCell 
dgvSearchResults.Columns.Add(objdatagridviewcolumn) 

Hiding Columns

The minimum width for a column is 5 and if you need to hide the column completely you can change the visible property in the Columns dialog box.

Sorting with a Particular Column

By default, users can sort the data in a DataGridView control by clicking the header of a text box column.
You can modify the SortMode property of specific columns to allow users to sort by other column types when it makes sense to do so.
You can also sort the data programmatically by any column, or by multiple columns.
The sort mode for each column is specified through the SortMode property of the column, which can be set to one of the following DataGridViewColumnSortMode enumeration values.

You might want to change the sort mode for a column that defaults to NotSortable if it contains values that can be meaningfully ordered.
For example, if you have a database column containing numbers that represent item states, you can display these numbers as corresponding icons by binding an image column to the database column. You can then change the numerical cell values into image display values in a handler for the System.Windows.Forms.DataGridView.CellFormatting event. In this case, setting the SortMode property to Automatic will enable your users to sort the column. Automatic sorting will enable your users to group items that have the same state even if the states corresponding to the numbers do not have a natural sequence. Check box columns are another example where automatic sorting is useful for grouping items in the same state.
You can sort a DataGridView programmatically by the values in any column or in multiple columns, regardless of the SortMode settings. Programmatic sorting is useful when you want to provide your own user interface (UI) for sorting or when you want to implement custom sorting. Providing your own sorting UI is useful, for example, when you set the DataGridView selection mode to enable column header selection. In this case, although the column headers cannot be used for sorting, you still want the headers to display the appropriate sorting glyph, so you would set the SortMode property to Programmatic.

Columns set to programmatic sort mode do not automatically display a sorting glyph. For these columns, you must display the glyph yourself by setting the System.Windows.Forms.DataGridViewColumnHeaderCell.SortGlyphDirection property. This is necessary if you want flexibility in custom sorting. For example, if you sort the DataGridView by multiple columns, you might want to display multiple sorting glyphs or no sorting glyph.

Although you can programmatically sort a DataGridView by any column, some columns, such as button columns, might not contain values that can be meaningfully ordered. For these columns, a SortMode property setting of NotSortable indicates that it will never be used for sorting, so there is no need to reserve space in the header for the sorting glyph.
When a DataGridView is sorted, you can determine both the sort column and the sort order by checking the values of the SortedColumn and SortOrder properties. These values are not meaningful after a custom sorting operation. For more information about custom sorting, see the Custom Sorting section later in this topic.
When a DataGridView control containing both bound and unbound columns is sorted, the values in the unbound columns cannot be maintained automatically. To maintain these values, you must implement virtual mode by setting the VirtualMode property to true and handling the CellValueNeeded and CellValuePushed events. For more information, see How to: Implement Virtual Mode in the Windows Forms DataGridView Control. Sorting by unbound columns in bound mode is not supported.

Programmatic Sorting

You can sort a DataGridView programmatically by calling its Sort method.
The Sort(DataGridViewColumn,ListSortDirection) overload of the Sort method takes a DataGridViewColumn and a ListSortDirection enumeration value as parameters. This overload is useful when sorting by columns with values that can be meaningfully ordered, but which you do not want to configure for automatic sorting. When you call this overload and pass in a column with a SortMode property value of System.Windows.Forms.DataGridViewColumnSortMode.Automatic, the SortedColumn and SortOrder properties are set automatically and the appropriate sorting glyph appears in the column header.

When the DataGridView control is bound to an external data source by setting the DataSource property, the Sort(DataGridViewColumn,ListSortDirection) method overload does not work for unbound columns. Additionally, when the VirtualMode property is true, you can call this overload only for bound columns. To determine whether a column is data-bound, check the IsDataBound property value. Sorting unbound columns in bound mode is not supported.

Custom Sorting

You can customize DataGridView by using the Sort(IComparer) overload of the Sort method or by handling the SortCompare event.

The Sort(IComparer) method overload takes an instance of a class that implements the IComparer interface as a parameter. This overload is useful when you want to provide custom sorting; for example, when the values in a column do not have a natural sort order or when the natural sort order is inappropriate. In this case, you cannot use automatic sorting, but you might still want your users to sort by clicking the column headers. You can call this overload in a handler for the ColumnHeaderMouseClick event if you do not use column headers for selection.
The Sort(IComparer) method overload works only when the DataGridView control is not bound to an external data source and the VirtualMode property value is false. To customize sorting for columns bound to an external data source, you must use the sorting operations provided by the data source. In virtual mode, you must provide your own sorting operations for unbound columns.

As an alternative to the Sort(IComparer) method overload, you can provide custom sorting by implementing a handler for the SortCompare event. This event occurs when users click the headers of columns configured for automatic sorting or when you call the Sort(DataGridViewColumn,ListSortDirection) overload of the Sort method. The event occurs for each pair of rows in the control, enabling you to calculate their correct order.

The SortCompare event does not occur when the DataSource property is set or when the VirtualMode property value is true.

Me.dataGridView1.Columns("Priority").SortMode = DataGridViewColumnSortMode.Automatic   

Sorting by a column - leave the current row highlighted but do not alter the scroll bar
maybe always leave the totoal frozen at the top ?

AllowSorting

This is a property of the DataGridTableStyle and indicates whether sorting is allowed on the grid table.
It has a default value of TRUE.

objDataGridTableStyle.AllowSorting = True 

When the AllowSorting property is True, a triangle appears in each column header indicating the direction of the sort.
The user can click on any column header to sort the grid by that column.
Clicking the column header a second time will automatically sort in the opposite direction.
This property overrides the AllowSorting property of the DataGrid object.

Custom Sorting

You can customise the sorting of your data by using the MouseDown and MouseUp events.

Private mbSortColumn As Boolean 

Private Sub dgrDataGrid_MouseDown(ByVal sender As Object, _ 
                                  ByVal e As System.Windows.Forms.MouseEventArgs) _ 
                                  Handles dgrDataGrid.MouseDown 

   Dim objDataGridHitTestInfo As DataGrid.HitTestInfo 

   'Only use left mouse button clicks as right might have shortcut menu
   If e.Button = MouseButtons.Left Then 
            
      'Perform a hit test to determine where the mousedown event occured.
      objDataGridHitTestInfo = dgrDataGrid.HitTest(e.X, e.Y) 
        
      If objDataGridHitTestInfo.Type = dgrDataGrid.HitTestType.ColumnHeader Then 
          mbSortColumn = True 
      End If 
   End If 
End Sub 

Private Sub dgrDataGrid_MouseUp(ByVal sender As Object, _ 
                                ByVal e As System.Windows.Forms.MouseEventArgs) _ 
                                Handles dgrDataGrid.MouseUp 

   Dim objDataGridHitTestInfo As DataGrid.HitTestInfo 
   Dim objDataTable As DataTable 
   Dim objDataView As DataView 
   Dim scolumnname As String 

        ' Use only left mouse button clicks.
   If e.Button = MouseButtons.Left And 
       mbSortColumn = True Then 

       mbSortColumn = False 'Reset mouse button state  
        
      ' Perform a hit test to determine where the mousedown event occured.
       objDataGridHitTestInfo = dataGrid.HitTest(e.X, e.Y) 
        
       ' If the mousedown event occured on a column header,
       ' then perform the sorting operation.
       If objDataGridHitTestInfo.Type = dgrDataGrid.HitTestType.ColumnHeader Then 

          objDataTable = dgrDataGrid.DataSource 
          objDataView = dgrDataTable.DefaultView 
          scolumnname = dataTable.Columns(hitTest.Column).ColumnName 
        
         ' If the sort property of the DataView is already the current column name, sort that in column descending order.
          ' Otherwise, sort on the column name.
          If dataView.Sort = scolumnname Then 
              dataView.Sort = scolumnname + " DESC" 
          Else 
              dataView.Sort = scolumnname 
          End If 
      End If 
   End If 
End Sub 

DataGridViewRow

You can access the rows by using the Rows collection

dgvDataGridView.Rows 

AllowUserToAddRows

If this is enabled a special row is added.
This row is included in the Rows collection

Hiding Rows

Can be very slow

objDataGridView.SuspendLayout 
objDataGridViewRow.Visible = False 
objDataGridView.ResumeLayout 

DataGridViewRowTemplate

Gets or sets the row that represents the template for all the rows.

Using a RowTemplate lets you create and initialise a DataGridViewRow for use as a template, including the row for new records if the AllowUserToAddRows property is true.

Useful if you are setting default values or a specific row height.

Adding Rows

Rows cannot be added to a DataGridView programmatically when the control is data bound.

Dim objDataGridViewRow As System.Windows.Forms.DataGridViewRow 

objDataGridView.Rows.Add() 
objDataGridViewRow = objDataGridView.Rows(objDataGridView.Rows.Count -1) 

objDataGridViewRow.Cells(0).Value = "first column" 
objDataGridViewRow.Cells(1).Value = "second column" 

objDataGridView.Rows.Add(New String() {"Parker", "Seattle"}) 

Alternating Row Shading

This enables you use style characteristics like foreground color and font, in addition to background color, to differentiate alternating rows.

DataGridView1.RowsDefaultCellStyle.BackColor = Color.Bisque 
DataGridView1.AlternatingRowsDefaultCellStyle.BackColor = Color.Beige 

The styles specified using the RowsDefaultCellStyle and AlternatingRowsDefaultCellStyle properties override the styles specified on the column and DataGridView level, but are overridden by the styles set on the individual row and cell level.

Bulk Addition

Do not use BeginEdit and EndEdit

The following line does not work ??

objDataGridView.Rows.Add(objDataGridViewRow) 

DataGridViewCell

This is the fundamental unit of interaction for the DataGridView
You can access cells by using the Cells collection of the DataGridViewRows class.

dgvDataGridViewRow.Cells(0) 

You can access the selected cells by using the SelectedCells collection

dgvDataGridViewRow.Cells(0) 

DataGridViewCell objects do not control their own appearance and painting features

Value

For a DataGridView that is not databound and not in virtual mode each cell stores its own value

Value (Databound)

For a DataGridView that is databound each cell does not know its actual value and must be looked up in the datasource.
The data type of each cell is automatically changed and this can be seen from the ValueType property.

FormattedValue

The FormattedValueType property determines the type that is used for display.
Most columns use String

Any time the FormattedValue is required the CellFormatting event is fired

If a cell cannot retrieve its formatted value correctly it raises the DataError event.

DataGridViewCellStyle

Always try and set the default cell style for the whole DataGridView control

dgvDataGridView.DefaultCellStyle = 

Dim highlightCellStyle As New DataGridViewCellStyle 
highlightCellStyle.BackColor = Color.Red 

Dim currencyCellStyle As New DataGridViewCellStyle 
currencyCellStyle.Format = "C" 
currencyCellStyle.ForeColor = Color.Green 

With Me.dataGridView1 
    .DefaultCellStyle.BackColor = Color.Beige 
    .DefaultCellStyle.Font = New Font("Tahoma", 12) 
    .Rows(3).DefaultCellStyle = highlightCellStyle 
    .Rows(8).DefaultCellStyle = highlightCellStyle 
    .Columns("UnitPrice").DefaultCellStyle = currencyCellStyle 
    .Columns("TotalPrice").DefaultCellStyle = currencyCellStyle 
End With 

The following are the list of objects and properties that can get or set DataGridViewCellStyle objects

DataGridView.DefaultCellStyle 
DataGridViewColumn.DefaultCellStyle 
DataGridViewRow.DefaultCellStyle 

DataGridView.RowsDefaultCellStyle 
DataGridView.AlternatingRowsDefaultCellStyle 
DataGridView.RowHeadersDefaultCellStyle 
DataGridView.ColumnHeadersDefaultCellStyle 

DataGridViewCell.Style 

DataGridViewColumn.InheritedStyle 
DataGridViewRow.InheritedStyle 
DataGridViewCell.InheritedStyle 

Getting the value of a style automatically instantiates a new DataGridViewCellStyle object if the property has not been previously set.
To avoid creating these accidentally you should check first using the following properties:

DataGridViewColumn.HasDefaultCellStyle 
DataGridViewRow.HasDefaultCellStyle 

DataGridViewCell.HasStyle 

DataGridViewTextBoxCell

This is a specialised type of DataGridViewCell that is used to display a single string of editable text.
When you derive from this class you need to overwrite the Clone method.

Properties

DataGridViewCheckBoxCell

Properties

if (checkboxCell.Value == true) 
{ 
} 

DataGridViewCellTemplate

Cell templates are instances of a DataGridViewCell derived class.

Making changes to the CellTemplate of a column will update the template and update all the cells in that column, refreshing the display if necessary.

DataTable

Linking a DataGridView directly to a DataTable

Never use this because it is a nightmare if you want to create a bespoke interface.

Rows cannot be added to a DataGridView programmatically when the control is data bound.
This can be done using the DataSource property of the DataGridView control.
The column headings will be automatically taken from the headings in the DataTable
After the DataGridView has been populated you need to then define the widths of the columns

When you bind a DataGridView control you can use the "AutoGenerateColumns" property to automatically generate default column types appropriate for the data types in the bound data sources.

Call clsDatabase.ConnectionOpen(gsConnectionString, gsSOLUTION_NAME) 

clsDatabase.mobjDataSet = New System.Data.DataSet() 

clsDatabase.gDataAdapter = New System.Data.OleDb.OleDbDataAdapter() 
clsDatabase.gDataAdapter.TableMappings.Add("Table", "TableName") 

clsDatabase.gsSQLQuery = "" 
clsDatabase.gsSQLQuery = clsDatabase.gsSQLQuery & " SELECT" 
clsDatabase.gsSQLQuery = clsDatabase.gsSQLQuery & " Columns 
clsDatabase.gsSQLQuery = clsDatabase.gsSQLQuery & " FROM" 
clsDatabase.gsSQLQuery = clsDatabase.gsSQLQuery & " TableName 

objdatacommand.Connection = clsDatabase.gDataConnection 
objdatacommand.CommandText = clsDatabase.gsSQLQuery 

clsDatabase.gDataAdapter.SelectCommand = objdatacommand 
irowsreturned = clsDatabase.gDataAdapter.Fill(clsDatabase.mobjDataSet, "TableName") 

dgvDataGridView.DataSource = clsDatabase.mobjDataSet.Tables("TableName").DefaultView 
dgvDataGridView.Columns(0).Width = 50 

Call clsDatabase.ConnectionClose(gsSOLUTION_NAME) 

The dataset object in your program is only a representation of the data in your original database. If the user makes any changes to this data, it is not written back to the original database unless you specifically instruct the data adapter object to make these changes

When you make a change to the data grid, the data grid automatically updates the dataset to which the data grid is bound.

Border and Gridlines

With the DataGridView control, you can customize the appearance of the control's border and gridlines to improve the user experience.
You can modify the gridline color and the control border style in addition to the border styles for the cells within the control.
You can also apply different cell border styles for ordinary cells, row header cells, and column header cells.

The gridline color is used only with the Single, SingleHorizontal, and SingleVertical values of the DataGridViewCellBorderStyle enumeration and the Single value of the DataGridViewHeaderBorderStyle enumeration. The other values of these enumerations use colors specified by the operating system. Additionally, when visual styles are enabled on Windows XP and the Windows Server 2003 family through the System.Windows.Forms.Application.EnableVisualStyles method, the GridColor property value is not used.

Me.dataGridView1.GridColor = Color.BlueViolet 
Me.dataGridView1.BorderStyle = BorderStyle.Fixed3D 

With Me.dataGridView1 
    .CellBorderStyle = DataGridViewCellBorderStyle.None 
    .RowHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single 
    .ColumnHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single 
End With 

Cell Styles

Each cell within the DataGridView control can have its own style, such as text format, background color, foreground color, and font. Typically, however, multiple cells will share particular style characteristics.

Groups of cells that share styles may include all cells within particular rows or columns, all cells that contain particular values, or all cells in the control. Because these groups overlap, each cell may get its styling information from more than one place. For example, you may want every cell in a DataGridView control to use the same font, but only cells in currency columns to use currency format, and only currency cells with negative numbers to use a red foreground color.

Multiple Select Checked ListBox

modAppSpecific

Public mobjDataTable As New System.Data.DataTable() 
Public mobjDataView As System.Data.DataView 

Public gdlgDialogName As frmDialog 
Public giDataGridRowIndex As Integer 

BET_DataGridName

Option Strict On 

Public Class BET_DataGridWorksheets 
   Inherits System.Windows.Forms.DataGrid 

   Private Const msMODULENAME As String = "BET_DataGrid" 

   Private mobjCOMException As System.Runtime.InteropServices.COMException 
   Private mobjException As Exception 

   '***************************************************************************************
   Protected Overrides Function ProcessCmdKey(ByRef msg As System.Windows.Forms.Message, _ 
                                              ByVal keyData As System.Windows.Forms.Keys) _ 
                                              As Boolean 

      Try 
         If clsError.ErrorFlag() = True Then Exit Function 

         clsDataGrid.MouseOrArrowKey = "ArrowKey" 

         Select Case msg.WParam.ToInt32 

            Case CType(System.Windows.Forms.Keys.Up, Integer) 
               Call CustomMouseUpEvent() 


            Case CType(System.Windows.Forms.Keys.Down, Integer) 
               Call CustomMouseDownEvent() 

         End Select 

         Call MyBase.ProcessCmdKey(msg, keyData) 

      Catch objCOMException As System.Runtime.InteropServices.COMException 
         mobjCOMException = objCOMException 
      Catch objException As Exception 
         mobjException = objException 

      Finally 
         If gbDEBUG = True Or _ 
            ((IsNothing(mobjCOMException) = False Or IsNothing(mobjException) = False)) Then 

            Call clsError.Handle("ProcessCmdKey", msMODULENAME, _ 
                 "respond to this event successfully.", _ 
                 mobjCOMException, mobjException) 
         End If 
      End Try 
   End Function 
   '***************************************************************************************
   Private Sub CustomMouseUpEvent() 

      Try 
         If clsError.ErrorFlag() = True Then Exit Sub 

         Dim irowno As Integer 

         'the first row index in the datagrid
         If giDataGridRowIndex = 0 Then Exit Sub 

         giDataGridRowIndex = giDataGridRowIndex - 1 

      Catch objCOMException As System.Runtime.InteropServices.COMException 
         mobjCOMException = objCOMException 
      Catch objException As Exception 
         mobjException = objException 

      Finally 
         If gbDEBUG = True Or _ 
            ((IsNothing(mobjCOMException) = False Or IsNothing(mobjException) = False)) Then 

            Call clsError.Handle("CustomMouseUpEvent", msMODULENAME, _ 
                 "respond to this event successfully.", _ 
                 mobjCOMException, mobjException) 
         End If 
      End Try 
   End Sub 
   '***************************************************************************************
   Private Sub CustomMouseDownEvent() 

      Try 
         If clsError.ErrorFlag() = True Then Exit Sub 

         Dim irowno As Integer 

         'the last row indes in the datagrid
         Call MsgBox("Number of rows : " & mobjDataView.Table.Rows.Count) 

         If giDataGridRowIndex = mobjDataView.Table.Rows.Count - 1 Then Exit Sub 

         giDataGridRowIndex = giDataGridRowIndex + 1 

      Catch objCOMException As System.Runtime.InteropServices.COMException 
         mobjCOMException = objCOMException 
      Catch objException As Exception 
         mobjException = objException 

      Finally 
         If gbDEBUG = True Or _ 
            ((IsNothing(mobjCOMException) = False Or IsNothing(mobjException) = False)) Then 

            Call clsError.Handle("CustomMouseDownEvent", msMODULENAME, _ 
                 "respond to this event successfully.", _ 
                 mobjCOMException, mobjException) 
         End If 
      End Try 
   End Sub 
   '***************************************************************************************
End Class 

frmDialog

Private Sub frmSheetManager_Load(ByVal sender As System.Object, _ 
                                 ByVal e As System.EventArgs) _ 
                                 Handles MyBase.Load 

Dim sacolumnsarray(,) As String 
Dim isheetnumber As Integer 
Dim sadataarray(,) As String 

   ReDim sacolumnsarray(1, 4) 

   sacolumnsarray(0, 0) = "CheckBox"     'Type  
   sacolumnsarray(0, 1) = "Include"      'Mapping Name  
   sacolumnsarray(0, 2) = ""             'Header Name  
   sacolumnsarray(0, 3) = "26"           'Width  
   sacolumnsarray(0, 4) = "Include"      'Registry Prefix  

   sacolumnsarray(1, 0) = "TextBox"      'Type  
   sacolumnsarray(1, 1) = "Name"         'Mapping Name  
   sacolumnsarray(1, 2) = "Name"         'Header Name  
   sacolumnsarray(1, 3) = "90"           'Width  
   sacolumnsarray(1, 4) = "Name"         'Registry Prefix  

   mobjDataTable = clsDataGrid.DataTableDefine("Worksheets", sacolumnsarray) 

   ReDim sadataarray(gApplication.Sheets.Count - 1, 1) 

   For isheetnumber = 1 To gApplication.Sheets.Count 

      objWorksjeet = CType(gApplication.Sheets(isheetnumber), Excel.Worksheet) 

      sadataarray(isheetnumber - 1, 0) = "TRUE" 

      sadataarray(isheetnumber - 1, 1) = objWorksheet.Name 

   Next isheetnumber 

   Call clsDataTable.InsertRowsFromArray(mobjDataTable.TableName, "Worksheets", sadataarray) 

   mobjDataView = New DataView(mobjDataTable) 

   mobjDataView.AllowNew = False 
   mobjDataView.AllowDelete = False 
   mobjDataView.AllowEdit = False 

   Me.dgrWorksheets.DataSource = mobjDataView 

   Call clsDataGrid.DataTableStyleDefine(mobjDataTable.TableName.ToString, _ 
                                         Me.dgrWorksheets, _ 
                                          sacolumnsarray) 
End Sub 

   Private Sub dgrWorksheets_Click(ByVal sender As Object, _ 
                                   ByVal e As System.EventArgs) _ 
                                   Handles dgrWorksheets.Click 

      Try 
         If clsError.ErrorFlag() = True Then Exit Sub 

         Dim objPoint As System.Drawing.Point = _ 
            Me.dgrWorksheets.PointToClient(System.Windows.Forms.Control.MousePosition) 

         Dim objDataGridHitTest As System.Windows.Forms.DataGrid.HitTestInfo = _ 
            Me.dgrWorksheets.HitTest(objPoint) 

         Dim objBindingManagerBase As System.Windows.Forms.BindingManagerBase = _ 
            Me.BindingContext(Me.dgrWorksheets.DataSource, Me.dgrWorksheets.DataMember) 

         If (clsDataGrid.CellChangedEvent = True) And _ 
            (objDataGridHitTest.Row < objBindingManagerBase.Count) And _ 
            (objDataGridHitTest.Type = System.Windows.Forms.DataGrid.HitTestType.Cell) Then 

            'this toggles the value of the checkbox
            Me.dgrWorksheets(objDataGridHitTest.Row, 0) = _ 
               Not CBool(Me.dgrWorksheets(objDataGridHitTest.Row, 0)) 

         End If 

      Catch objCOMException As System.Runtime.InteropServices.COMException 
         mobjCOMException = objCOMException 
      Catch objException As Exception 
         mobjException = objException 

      Finally 
         If gbDEBUG = True Or _ 
            ((IsNothing(mobjCOMException) = False Or IsNothing(mobjException) = False)) Then 

            Call clsError.Handle("dgrWorksheets_Click", msMODULENAME, _ 
                 "respond to this event successfully.", _ 
                 mobjCOMException, mobjException) 
         End If 
      End Try 
   End Sub 
   '*************************************************************************************
   Private Sub dgrWorksheets_CurrentCellChanged(ByVal sender As Object, _ 
                                                ByVal e As System.EventArgs) _ 
                                                Handles dgrWorksheets.CurrentCellChanged 

      Try 
         If clsError.ErrorFlag() = True Then Exit Sub 

         Dim itempdatagridrowindex As Integer 
         Dim irowno As Integer 

         If clsDataGrid.MouseOrArrowKey.Length = 0 Then 
            clsDataGrid.MouseOrArrowKey = "Mouse" 
         End If 

         Dim objPoint As System.Drawing.Point = _ 
            Me.dgrWorksheets.PointToClient(System.Windows.Forms.Control.MousePosition) 

         Dim objDataGridHitTest As System.Windows.Forms.DataGrid.HitTestInfo = _ 
            Me.dgrWorksheets.HitTest(objPoint) 

         If clsDataGrid.MouseOrArrowKey = "Mouse" Then 
            itempdatagridrowindex = objDataGridHitTest.Row() 
         Else 
            itempdatagridrowindex = -1 
         End If 

         If (itempdatagridrowindex > -1) Then 
            giDataGridRowIndex = itempdatagridrowindex 

            irowno = CInt(Me.dgrWorksheets(giDataGridRowIndex, 2)) 
         End If 

         clsDataGrid.MouseOrArrowKey = "" 

      Catch objCOMException As System.Runtime.InteropServices.COMException 
         mobjCOMException = objCOMException 
      Catch objException As Exception 
         mobjException = objException 

      Finally 
         If gbDEBUG = True Or _ 
            ((IsNothing(mobjCOMException) = False Or IsNothing(mobjException) = False)) Then 

            Call clsError.Handle("dgrWorksheets_CurrentCellChanged", msMODULENAME, _ 
                 "respond to this event successfully.", _ 
                 mobjCOMException, mobjException) 
         End If 
      End Try 

   End Sub 

#Region " Windows Form Designer generated code "

Change the control declaration to refer to the new custom control.

Friend WithEvents dgrWorksheets As BET_DataGridName 
   Me.dgrWorksheets = New BET_DataGridName() 

Columns and Column Order

The correspondence between a particular column in a DataTable, and a particular DataGridColumnStyle object is made through the DataGridColumnStyle.MappingName property. This property is the one required property that is needed to be set when creating a DataGridColumnStyle. Other DataGridColumnStyle properties of interest include Header, ReadOnly and Width.
The following is a modified Form Load event handler that will create the DataGridTableStyle (step 1), create the DataGridColumnStyles and add them to the GridColumnStyles collection (step 2), and finally, add the DataGridTableStyle to the DataGrid.TableStyles property (step 3).

Private Sub MyForm_Load(ByVal sender As System.Object, _ 
                        ByVal e As System.EventArgs) Handles MyBase.Load 
                        Me.SqlDataAdapter1.Fill(Me.DataSet11) 

Dim tableStyle As New DataGridTableStyle() 
Dim discontinuedCol As New DataGridBoolColumn() 
Dim column As New DataGridTextBoxColumn() 

   tableStyle = New DataGridTableStyle() 
   tableStyle.MappingName = "Products" 

   discontinuedCol.MappingName = "Discontinued" 
   discontinuedCol.HeaderText = "" 
   discontinuedCol.Width = 30 
   discontinuedCol.AllowNull = False 
   tableStyle.GridColumnStyles.Add(discontinuedCol) 

   column = New DataGridTextBoxColumn() 
   column.MappingName = "ProductID" 
   column.HeaderText = "ID" 
   column.Width = 30 
   tableStyle.GridColumnStyles.Add(column) 

   column = New DataGridTextBoxColumn() 
   column.MappingName = "ProductName" 
   column.HeaderText = "Name" 
   column.Width = 140 
   tableStyle.GridColumnStyles.Add(column) 

   'Add the tablestyle to the datagrid
   Me.DataGrid1.TableStyles.Add(tableStyle) 
End Sub 

Change Click Behavior on a Discontinued Row

Move focus to a particular column when the user selects any cell the focus is moved to the first column
Add a handler for the CurrentCellChanged event. In that handler, if the value in the first column is true then set the current cell to the first column.

Private Sub dgrDataGrid_CurrentCellChanged(ByVal sender As Object, _ 
                                           ByVal e As System.EventArgs) _ 
                                           Handles dgrDataGridCurrencies.CurrentCellChanged 

Dim objCheckBoxValue As Object = Me.dgrDataGrid(Me.DataGrid1.CurrentRowIndex, 0) 
Dim bCheckBoxValue As Boolean = CBool(objCheckBoxValue) 

  If (bCheckBoxValue = True) Then 
     Me.dgrDataGrid.CurrentCell = _ 
         New System.Windows.Forms.DataGridCell(Me.dgrDataGrid.CurrentRowIndex, 0) 
   End If 
End Sub 

Changing Cell BackColor, ForeColor and Font

To customize the way a DataGrid cell is drawn, it is necessary to override the Paint method in a derived DataGridTextBoxColumn class. When the DataGrid with a DataGridTableStyle associated with it needs to paint a cell, it calls the Paint method of the DataGridTextBoxColumn. The arguments in this call include a ForeBrush and BackBrush that controls the colors used to draw the cell. Therefore, to control the colors used to paint a cell on a per cell basis, it is possible to override the virtual Paint method of the DataGridTextBoxColumn class, and change the brushes according to the particular cell being drawn.

The following strategy is to add an event to the derived DataGridTextBoxColumn. In the derived Paint method, this event is fired to allow listeners to provide the BackColor and ForeColor to be used for the cell being painted. Once this event is in place, it is only necessary to write an event handler to control the color of a grid cell. Also derived are special EventArgs to provide the event listener with the row index and column index values, and to allow the event listener to set the color properties.

Creating the Event Arguments Class
In Solution Explorer, right-click the project, and add a new class named DataGridFormatCellEventArgs, which is inherited from EventArgs. The following is a list of the public properties of this class and a note on how they are used. The first three properties are passed into the event handler through the argument; the last seven properties are set by the event listener to indicate how the cell should be drawn.

Column (Integer): The column number of the cell being painted.
Row (Integer): The row number of the cell being painted.
CurrentCellValue (Object): The current cell value.
TextFont (Font): The font to be used to draw text in the cell.
BackBrush (Brush): The brush used to paint the cell's background.
ForeBrush (Brush): The brush used to paint the text in the cell.
TextFontDispose (Boolean): True to call the TextFont.Dispose.
BackBrushDispose (Boolean): True to call the BackBrush.Dispose.
ForeBrushDispose (Boolean): True to call the ForeBrush.Dispose.
UseBaseClassDrawing (Boolean): True to call the MyBase.Paint.
The dispose properties included as part of the DataGridFormatCellEventArgs are set by the listener if the Paint override should call the Dispose method on the objects that implement IDisposable. For example, if dynamically creating a BackBrush every time a grid cell is drawn, use the Paint method to call Dispose on the brush after it is finished with its drawing. On the other hand, if a single brush is created and cached that will be used to provide the BackBrush for some cells, it is not desirable to have the Paint method to call Dispose on the cached brush. These dispose properties let the listener tell the Paint override how to handle the Dispose calls.

The following is how the actual class code should appear. Before the class definition, add the delegate that determines the signature of the event handler required for the SetCellFormat event that will be defined as part of the derived DataGridTextBoxColumn.

Public Delegate Sub FormatCellEventHandler( _ 
     ByVal sender As Object, _ 
     ByVal e As DataGridFormatCellEventArgs) 

Public Class DataGridFormatCellEventArgs 
    Inherits EventArgs 

    Public Sub New(ByVal row As Integer, _ 
       ByVal col As Integer, _ 
       ByVal cellValue As Object) 
    End Sub 'New  
End Class 

Creating the Derived DataGridTextBoxColumn

The next step is to add the class code for the derived DataGridTextBoxColumn. This is done in the same way, right-clicking the project in Solution Explorer and adding a new class named FormattableTextBoxColumn. To add the stub for the Paint override, select (Overrides) in the left drop-down list on top of the editing window, and then select the second Paint method (the one with seven arguments) listed in the right drop-down list at the top of the editing window. The following is what the code will look like.

Note Notice the SetCellFormat event declaration is also added, using the event delegate FormatCellEventHandler that was defined in the previous class file.

Public Class FormattableTextBoxColumn 
    Inherits DataGridTextBoxColumn 

    Public Event SetCellFormat As FormatCellEventHandler 

 Protected Overloads Overrides Sub Paint(………) 
        
    End Sub 'Paint     
End Class 

Implementing the Paint Override

The first thing to do in the Paint override is to fire the SetCellFormat event. It is through this event that an event listener will provide the format preferences that are to be used with this cell. The steps are to create the DataGridFormatCellEventArgs, initializing the row, column and current value, and then raise the event with this argument. Finally, after the event has been raised, query the event argument to see what formatting actions need to be done.

Raising the Event

The following is the code snippet that creates the argument and fires the event. The variables source and rowNum are passed into the Paint method.

Dim e As DataGridFormatCellEventArgs = Nothing 

   'Get the column number
    Dim col As Integer = _ 
     Me.DataGridTableStyle.GridColumnStyles.IndexOf(Me) 
    
'Create the eventargs object
 e = New DataGridFormatCellEventArgs( _ 
       rowNum, col, _ 
       Me.GetColumnValueAtRow([source], rowNum)) 

   'fire the formatting event
   RaiseEvent SetCellFormat(Me, e) 

Color Formatting

Once the event has returned, inspect the properties of the DataGridFormatCellEventArgs object to find out about the colors in which the cell should appear. The two brushes, foreBrush and backBrush, used to draw the cell are passed as arguments to the Paint method. To change the cell colors, swap the old brushes for the new brushes before calling the Paint method's base class implementation. The following is a code snippet that illustrates this idea:

' assume we will call the baseclass

Dim callBaseClass As Boolean = True 

   ' check the brushes returned from the event
   If Not (e.BackBrush Is Nothing) Then 
        backBrush = e.BackBrush 
   End If 
   If Not (e.ForeBrush Is Nothing) Then 
        foreBrush = e.ForeBrush 
   End If 

   ' check the UseBaseClassDrawing property
   If Not e.UseBaseClassDrawing Then 
            callBaseClass = False 
   End If 
   
   If callBaseClass Then 
        MyBase.Paint(g, bounds, _ 
          [source], rowNum, backBrush, _ 
          foreBrush, alignToRight) 
   End If 

The previous snippet sets the brushes depending upon the properties of the DataGridFormatCellEventArgs object. Depending upon the UseBaseClassDrawing value, it calls the base class. Calling the base class with the modified brushes is how to affect the cell color. Recall that this method will be called for each cell in a column as it is drawn.

Handling the TextFont Property

Trying to change the font used to draw in the cell adds a real complication to the Paint override. The reason is that the font used to draw the text is not a simple parameter passed as an argument in the Paint method. Instead, the font used to draw the cell text is originally gotten from the DataGrid.Font property. But this font is cached, and is not reset from the DataGrid.Font property for each cell. Thus, the first impulse, dynamically changing DataGrid.Font for each cell does not work. Therefore, to change the font of the cell, it is necessary to actually draw the string so that the font can be specified. Doing so adds significant work to try to mimic exactly the output of the standard DataGrid. The example will not go to extremes in this respect, but will be satisfied to get similar output, but not exactly the same output as with the unaltered DataGrid. The following is the code snippet that is used to implement drawing the string with a newly specified font.

'if TextFont set, then must call drawstring
If Not (e.TextFont Is Nothing) Then 
    Try 
        Dim charWidth As Integer = _ 
            Fix(Math.Ceiling(g.MeasureString("c", _ 
                e.TextFont, 20, _ 
                StringFormat.GenericTypographic).Width)) 
        Dim s As String = _ 
           Me.GetColumnValueAtRow([source], _ 
                 rowNum).ToString() 
        Dim maxChars As Integer = _ 
           Math.Min(s.Length, bounds.Width / charWidth) 

        Try 
            g.FillRectangle(backBrush, bounds) 
            g.DrawString(s.Substring(0, maxChars), _ 
                e.TextFont, foreBrush, _ 
                bounds.X, bounds.Y + 2) 
        Catch ex As Exception 
              System.Console.WriteLine(ex.Message.ToString()) 
        End Try 
    Catch 'empty catch  
    End Try 
    callBaseClass = False 
End If 

The first part of the code approximates the number of characters that can be displayed in the current cell width. It does so by approximating an average character size, and dividing this value into the cell width. It would be possible to do this more rigorously—repeatedly calling MeasureString to get the exact number of characters that would fit—but doing so makes the output significantly different than what the default DataGrid produces. Using this average character size approach is much quicker, and gives results much closer to the default DataGrid.

After getting the number of characters, draw the background and call Graphics.DrawString passing it the font and brush desired for use. Finally, set the callBaseClass flag so the baseclass Paint method is not later called, undoing all of the previous work.

Using the New FormattableTextBoxColumn Class

To use the newly derived column, go back to the form code, and swap out the occurrences of DataGridTextBoxColumn with FormattableTextBoxColumn. Then for each column, wire up the listener for the SetCellFormat event exposed by the derived class. There exists the option of using a different event handler for each column. But the requirements (coloring rows) allow the use of the same handler for all the columns. The following is the code for the typical column after these changes:

'ProductName
column = New FormattableTextBoxColumn() 
column.MappingName = "ProductName" 
column.HeaderText = "Name" 
column.Width = 140 
AddHandler column.SetCellFormat, AddressOf FormatGridRow 
tableStyle.GridColumnStyles.Add(column) 

Notice that an instance of a derived class is now being created, FormattableTextBoxColumn. Also, a handler is added, FormatGridRow, for the SetCellFormat event.

The SetCellFormat Event Handler

In the SetCellFormat handler, the brushes used to set the forecolor and backcolor of the cell whose row and column indexes are passed in through the event arguments will be set. If the cell is on the current row of the grid, use one set of colors and font. If the cell is on a row that has the Discontinued Boolean value set to true, use another set of colors. The following is the code that declares and defines these cached GDI+ objects.

'form variables to cache GDI+ objects
Private disabledBackBrush As Brush 
Private disabledTextBrush As Brush 
Private currentRowFont As Font 
Private currentRowBackBrush As Brush 

' In Form1_Load create and cache some GDI+ objects.
Me.disabledBackBrush = _ 
  New SolidBrush(SystemColors.InactiveCaptionText) 
Me.disabledTextBrush = _ 
  New SolidBrush(SystemColors.GrayText) 
Me.currentRowFont = _ 
  New Font(Me.DataGrid1.Font.Name, _ 
           Me.DataGrid1.Font.Size, _ 
           FontStyle.Bold) 
Me.currentRowBackBrush = Brushes.DodgerBlue 

In the code for the event handler, members of the DataGridFormatCellEventArgs value that are passed to display particular rows with special effects will be set. Discontinued rows will be grayed out, and the current row will be displayed with a DodgerBlue background using a bold font. The following is the handler that will implement these effects:

Private Sub FormatGridRow(ByVal sender As Object, _ 
        ByVal e As DataGridFormatCellEventArgs) 
    Dim discontinuedColumn As Integer = 0 
    ' Conditionally set properties in e depending upon e.Row and e.Col.
    Dim discontinued As Boolean = CBool( _ 
       IIf(e.Column <> discontinuedColumn, _ 
       Me.DataGrid1(e.Row, discontinuedColumn), _ 
       e.CurrentCellValue)) 
    ' Check if discontinued?
    If e.Column > discontinuedColumn AndAlso _ 
CBool(Me.DataGrid1(e.Row, discontinuedColumn)) Then 
         e.BackBrush = Me.disabledBackBrush 
         e.ForeBrush = Me.disabledTextBrush 
    ' current row?
    ElseIf e.Column > discontinuedColumn AndAlso _ 
           e.Row = Me.DataGrid1.CurrentRowIndex Then 
         e.BackBrush = Me.currentRowBackBrush 
         e.TextFont = Me.currentRowFont 
    End If 
End Sub 

Recall that there are actually several FormattableTextBoxColumn objects in the DataGrid.TableStyle(0).GridColumnStyles collection. In fact, every column, except the Boolean column, is using one of these objects. In addition, each of these objects has a SetCellFormat event, to which is being listened. However, each of these events is using the same handler, FormatGridRow, which was previously listed. Thus, the same formatting logic is being applied to every cell (except the Boolean cell) in a row. Therefore, the formatting is effectively setting row styles in that all cells in the row will show the same formatting behavior, even though the formatting is being done on a cell-by-cell basis.

The following is a picture of the grid at this point. Notice that the checked rows are grayed out, showing the item is discontinued, and the current row is DodgerBlue with a bold font.

The initial display looks pretty good. But there is a small problem that needs some effort to handle. The problem is that a click on a checked first column unchecks the cell properly, but does not redraw the row. This row needs to be refreshed anytime the check value changes. To handle this problem, it is necessary to derive from DataGridBooleanColumn and add an event handler that fires an event anytime the bool value changes. This will allow reaction to the changing click, and forces the row to be redrawn reflecting the new click value.

Adding a Boolean Column with a Value Changed

The Event Arguments
Start by adding a new class derived from EventArgs that holds the information the BoolValueChanged event will require. In particular, properties will be added that give the row and column of the cell being changed, as well as add properties to the new Boolean value. The following is the BoolValueChangedEventArgs class. The missing implementation uses private fields only to shadow the public properties with the fields being initialized in the constructor. The delegate will also be defined, BoolValueChangedEventHandler, for this event at the beginning of this file.

Public Delegate Sub BoolValueChangedEventHandler( _ 
       ByVal sender As Object, _ 
       ByVal e As BoolValueChangedEventArgs) 

Public Class BoolValueChangedEventArgs 
    Inherits EventArgs 
    
    Public Sub New(ByVal row As Integer, _ 
                   ByVal col As Integer, _ 
                   ByVal val As Boolean) 
           . . . 
    End Sub 'New  

    Public Property Column() As Integer 
           . . . 
 End Property 

    Public Property Row() As Integer 
         . . . 
    End Property 

    Public ReadOnly Property BoolValue() As Boolean 
           . . . 
    End Property 
End Class 'BoolValueChangedEventArgs  

The Derived DataGridBoolColumn Class

Now for the derived class, ClickableBooleanColumn, three methods will be overridden to handle different aspects of monitoring the Boolean value in the cell. The first override is Edit. This method is called when a cell needs to go into edit mode. In the override, some private field members will be set to reflect the current Boolean state as well as the fact that the current mode is in edit mode. The second override is the same Paint method that was previously used in FormattableTextBoxColumn. Here, instead of trying to modify the cell appearance, this method is used to track the change in the Boolean value, and to raise the BoolValueChanged event if it does change. The third override is the Commit method. This method is called when the editing is complete, and the value should be committed to the datasource. This method is used to turn off the fields that were set in the Edit override.

There are some technical points that need to be handled. The Boolean value can change because of a click in the cell, or a pressed spacebar, while the cell has focus. The helper method, ManageBoolValueChanging, is used to monitor these possibilities. Furthermore, it raises the BoolValueChanged event if the value is changed. To monitor the mouse click, the ManageBoolValueChanging checks the Control.MousePosition and Control.MouseButtons shared (static) properties. However, checking the KeyState of the spacebar is problematic. Resort to an Interop call into Win32 API GetKeyState to handle this problem.

The following is the code for the class: 

Public Class ClickableBooleanColumn 
    Inherits DataGridBoolColumn 

    'changed event
    Public Event BoolValueChanged _ 
         As BoolValueChangedEventHandler 

    'set variables to start tracking bool changes
    Protected Overloads Overrides Sub Edit(. . .) 
        Me.lockValue = True 
        Me.beingEdited = True 
        Me.saveRow = rowNum 
        Me.saveValue = CBool( _ 
           MyBase.GetColumnValueAtRow( _ 
                    [source], rowNum)) 
        MyBase.Edit(. . .) 
    End Sub 'Edit  

    'overridden to handle BoolChange event
    Protected Overloads Overrides Sub Paint(. . .) 
        Dim colNum As Integer = _ 
           Me.DataGridTableStyle.GridColumnStyles.IndexOf(Me) 

        'used to handle the boolchanging
        ManageBoolValueChanging(rowNum, colNum) 

        MyBase.Paint(. . .) 

    End Sub 'Paint  

    'turn off tracking bool changes
    Protected Overrides Function Commit(. . .) As Boolean 
        Me.lockValue = True 
        Me.beingEdited = False 
        Return MyBase.Commit(dataSource, rowNum) 
    End Function 'Commit  

    'fields to track bool value
    Private saveValue As Boolean = False 
    Private saveRow As Integer = -1 
    Private lockValue As Boolean = False 
    Private beingEdited As Boolean = False 
    Public Const VK_SPACE As Integer = 32 

    'needed to get the space bar changing of the bool value
    <System.Runtime.InteropServices.DllImport("user32.dll")> _ 
    Shared Function GetKeyState( _ 
           ByVal nVirtKey As Integer) As Short 
    End Function 

    'fire the bool change event if the value changes
    Private Sub ManageBoolValueChanging( _ 
                ByVal rowNum As Integer, _ 
                ByVal colNum As Integer) 
        Dim mousePos _ 
            As Point = Me.DataGridTableStyle.DataGrid.PointToClient( _ 
                       Control.MousePosition) 
        Dim dg As DataGrid = Me.DataGridTableStyle.DataGrid 
        Dim isClickInCell As Boolean = _ 
            Control.MouseButtons = MouseButtons.Left AndAlso _ 
            dg.GetCellBounds(dg.CurrentCell).Contains(mousePos) 

        Dim changing As Boolean = _ 
            dg.Focused AndAlso isClickInCell _ 
            OrElse GetKeyState(VK_SPACE) < 0 
        ' or spacebar
        If Not lockValue AndAlso _ 
                  beingEdited AndAlso _ 
                  changing AndAlso _ 
                  saveRow = rowNum Then 
            saveValue = Not saveValue 
            lockValue = False 

            'fire the event
            Dim e As New BoolValueChangedEventArgs( _ 
                          rowNum, colNum, saveValue) 
            RaiseEvent BoolValueChanged(Me, e) 
        End If 
        If saveRow = rowNum Then 
            lockValue = False 
        End If 
    End Sub 'ManageBoolValueChanging  
End Class 

Using the ClickableBooleanColumn

To use the special column style, create an instance of it when setting up the columnstyle for the discontinuedCol. A handler for the new BoolValueChanged event will also be added.

'    Discontinued.
Dim discontinuedCol As New ClickableBooleanColumn() 
discontinuedCol.MappingName = "Discontinued" 
discontinuedCol.HeaderText = "" 
discontinuedCol.Width = 30 
' turn off tristate
discontinuedCol.AllowNull = False 
AddHandler discontinuedCol.BoolValueChanged, _ 
AddressOf BoolCellClicked 
tableStyle.GridColumnStyles.Add(discontinuedCol) 

The BoolValueChanged Event Handler

In the event handler, the row must be forced to be redrawn using the new value of the Boolean cell. Anytime the Boolean value changes, the event handler invalidates the rectangle associated with a row to reflect the proper format. To force a redraw of a row, use a RefreshRow helper method. In the event handler, the Boolean value is forced to be stored by ending the edit mode. Doing so allows the FormatGridRow method to obtain the proper value of the Boolean cell. Without this call, only the initial value of the cell is available through the indexed DataGrid.

Private Sub BoolCellClicked(ByVal sender As Object, _ 
            ByVal e As BoolValueChangedEventArgs) 
    Dim g As DataGrid = Me.DataGrid1 
    Dim discontinuedCol As New _ 
         ClickableBooleanColumn = _ 
         g.TableStyles(0).GridColumnStyles("Discontinued")  
    g.EndEdit(discontinuedCol, e.Row, False) 
    RefreshRow(e.Row) 
    g.BeginEdit(discontinuedCol, e.Row) 
End Sub 

' Forces a repaint of given row.
Private Sub RefreshRow(ByVal row As Integer) 
    Dim r As Rectangle = _ 
        Me.dataGrid1.GetCellBounds(row, 0) 
    r = New Rectangle(r.Right, r.Top, _ 
        Me.dataGrid1.Width, r.Height) 
   Me.dataGrid1.Invalidate(r) 
End Sub 'RefreshRow  

There is one last problem to handle before clicking the check box to be certain that the cell behaves as expected with the row changing colors with each click. If a checkbox is clicked that is not checked and is not on the current row, then the click sets the row in the current row colors, instead of the discontinued colors. Furthermore, the problem appears strictly to be a refresh problem because dragging the grid on and off the display will cause the row to be redrawn using the expected discontinued format. This refresh problem can be handled by forcing the row to be refreshed during the existing dataGrid1_Click event handler. In that event, the code is executed to change the Boolean value, and also to refresh the row.

If afterCurrentCellChanged AndAlso _ 
   hti.Row < bmb.Count AndAlso _ 
   hti.Type = DataGrid.HitTestType.Cell AndAlso _ 
   hti.Column = 0 Then 
        Me.DataGrid1(hti.Row, 0) = _ 
            Not CBool(Me.DataGrid1(hti.Row, 0)) 
        RefreshRow(hti.Row) 
End If 

Adding Row-Dependent ToolTips

The Windows Forms ToolTip class can be used to add a ToolTip for an entire DataGrid. To do so, drag the ToolTip component onto the Form and set the ToolTip property that is added to every control on the form. However, implementing a ToolTip in this manner does not allow the tip to be varied when moving from row to row (or cell to cell) in the DataGrid. The goal is to display a ToolTip that can be varied from row to row. Using the same strategy, ToolTips could be implemented that vary from cell to cell or column to column.

Start by adding two fields to the Form class, hitRow and ToolTip1. These fields are initialized in Form1_Load, and are dynamically changed in the dataGrid1_MouseMove event handler that was added. In the MouseMove, check that the cursor is over a new row, and if so, reset the ToolTip with different text. See the following code example:

    Private hitRow As Integer 
    Private toolTip1 As System.Windows.Forms.ToolTip 

' In Form1_Load
    Me.hitRow = -1 
    Me.toolTip1 = New ToolTip() 
    Me.toolTip1.InitialDelay = 300 
    AddHandler Me.DataGrid1.MouseMove, _ 
          AddressOf dataGrid1_MouseMove 

Private Sub dataGrid1_MouseMove( _ 
        ByVal sender As Object, _ 
        ByVal e As MouseEventArgs) 

   Dim g As DataGrid = Me.dataGrid1 
   Dim hti As DataGrid.HitTestInfo = _ 
              g.HitTest(New Point(e.X, e.Y)) 
   Dim bmb As BindingManagerBase = _ 
            Me.BindingContext(g.DataSource, g.DataMember) 
   If hti.Row < bmb.Count AndAlso _ 
      hti.Type = DataGrid.HitTestType.Cell AndAlso _ 
      hti.Row <> hitRow Then 
       If Not (Me.toolTip1 Is Nothing) AndAlso _ 
            Me.toolTip1.Active Then 
            Me.toolTip1.Active = False 'turn it off  
       End If 
       Dim tipText As String = "" 
       If CBool(Me.DataGrid1(hti.Row, 0)) Then 
           tipText = Me.DataGrid1(hti.Row, 2).ToString() & _ 
                " discontinued" 
           If tipText <> "" Then 
               'new hit row
                hitRow = hti.Row 
                Me.toolTip1.SetToolTip(Me.DataGrid1, tipText) 
                ' make it active so it can show
                Me.toolTip1.Active = True 
            Else 
                hitRow = -1 
            End If 
        Else 
            hitRow = -1 
        End If 
    End If 
End Sub 'dataGrid1_MouseMove  

Conclusion

The final DataGrid uses two derived DataGridColumnStyles to handle cell formatting and monitor Boolean value changes. The formatting is accomplished by overriding the derived classes' Paint method, and raising an event to allow a listener to furnish format information based on a row and column index. The derived class that manages Boolean values also overrides the Paint method, firing an event when the value changes at this point; in addition, it requires Edit and Commit overrides to fully manage this task.

Also used are form level events to control DataGrid behavior. The DataGrid.CurrentCellChanged event was used to force the current cell to a particular cell in the row, no matter which cell in the row was clicked. The DataGrid.Clicked event was used to make the CheckBox column responds to the first click, instead of requiring two clicks to change its value. Finally, the DataGrid.MouseMove event was used to make ToolTips dynamic by changing from row to row.

There are two samples accompanying this article in the attached download (see link at the top). The first one, CustomGrid, contains the VB .NET project that served as the source for all the code snippets in this discussion. The second, CustomGridA, contains two projects, one VB .NET and the other C#. The C# project is more involved than the one used in this discussion, but generally follows the same flow.

The KeyUp, KeyPress and KeyDown events of the DataGrid do not fire when if you are in a cell.

Skip Columns When Tabbing

You can solve this problem by handling the DataGrid's CurrentCellChanged event, and simulate a Tab keypress when the user selects an "inaccessible" column.

Enable the column-skipping mechanism for the input grid and for the columns with the specified index
save the array of column indexes in the grid's Tag property
attach the grid's CurrentCellChanged event to the GenDataGrid_CurrentCellChanged event handler

Public Sub EnableDataGridColumnSkip(ByVal grid As DataGrid, _ 
                                    ByVal ParamArray columnsToSkip() As Integer) 
    grid.Tag = columnsToSkip 

    AddHandler grid.CurrentCellChanged, AddressOf GenDataGrid_CurrentCellChanged 
End Sub 

Disable the column-skipping mechanism for the input grid
' detach the grid's CurrentCellChanged event from the GenDataGrid_CurrentCellChanged event handler

Public Sub DisableDataGridColumnSkip(ByVal grid As DataGrid) 
    RemoveHandler grid.CurrentCellChanged, AddressOf GenDataGrid_CurrentCellChanged 
End Sub 

Handle the grid's CurrentCellChanged, to skip the columns whose index is found in the array stored in grid's Tag property
cast the generic sender Object to a DataGrid
cast the grid's Tag to an array of Integers, that contains the indexes of the columns to skip
get the index of the current column
if the current column's index is found in the columnsToSkip array, simulate a TAB key press,

Public Sub GenDataGrid_CurrentCellChanged(ByVal sender As Object, _ 
                                          ByVal e As System.EventArgs) 
    Dim grid As DataGrid = DirectCast(sender, DataGrid) 
    Dim columnsToSkip() As Integer = DirectCast(grid.Tag, Integer()) 
    Dim currColIndex As Integer = grid.CurrentCell.ColumnNumber 

    ' so that the focus is moved to the next column in the same row, or to the next row if this is the last column
    If Array.IndexOf(columnsToSkip, currColIndex) > -1 Then 
        SendKeys.Send("{TAB}") 
    End If 
End Sub