A DataView is basically similar to a conventional database view, which is just a view of a datatable with different sorting and filtering criteria.
DataViews represent a customised view of a DataTable ideal for sorting, filtering, searching, editing etc
A DataView is similar to a live view on a DataTable, which allows programmers to set a sort order and filter on a view of the table.
This is just a view over an existing DataTable.
This gives you the same filtering and sorting capabilities as the DataTable.Select method.
Creating a DataView Object
Dim objDataView As System.Data.DataView
objDataView = New System.Data.DataView
objDataView.Table = objDataSet.Tables("Projects")
This allows you to specify an expression similar to a SQL WHERE clause.
objDataView.RowFilter = "FirstName = 'Russell'"
objDataView.RowFilter = "FirstName LIKE 'M*'"
objDataView.RowFilter = "Len(LastName) > 8"
objDataView.RowStateFilter = DataViewRowState.Deleted
objDataView.Sort = "FirstName DESC"
Adding and Deleting
You can add, delete and modify rows in a DataView by using the same methods you would use with the DataTable.
Gets the number of records in the DataView after RowFilter and RowStateFilter have been applied.
You can also use the Find method to retrieve a DataRow given its primary key value.
Both these methods require that a primary key has been defined on the DataTable.
If the primary key exists then a DataRow object is returned. If the primary key does not exist then a Null value is returned.
objDataRow = objDataTable.Rows.Find(100)
You can also use the Contains method to search for character-based single words or phrases.
bfound = objDataTable.Rows.Contains(100)
You can also use the Find and FindRows methods of the DataView object.
Both these methods rely on the DataView being sorted by the column entry you are trying to find.
objDataView.Sort = "FirstName"
iRowIndex = objDataView.Find("Russell")
A DataView contains a collection of DataRowView objects which are views over the rows in the underlying DataTable.
Dim objDataRowView As System.Data.DataRowView
For Each objDataRowView In objDataTableConsolidation.DefaultView
sValue = objDataRowView.Item("ColumnName").ToString
This binds the default DataView from a particular table and binds it to a DataGrid control.
Me.dgrDataGrid.DataSource = objDataSet.Tables("TableName").DefaultView
This obtains the DataView that is associated with a DataGrid.
Dim objDataView As System.Data.DataView
objDataView = CType(Me.dgrDataGrid.DataSource, System.Data.DataView)
|CurrentRows||Includes unchanged, new and modified rows. Deleted rows are not included.|
|OriginalRows||All the rows as they were after the most recent AcceptChanges or RejectChanges method. This includes unchanged and deleted rows. Added rows are not included.|
|Unchanged||Unchanged rows only|
|Added||Added rows only|
|Deleted||Deleted rows only|
|ModifiedCurrent||Changed rows only. Columns contain the current (modified) value.|
|ModifiedOriginal||Changed rows only. Columns contain the original value.|
|None||No rows are returned.|
|AllowDelete||True if rows can be deleted.|
|AllowEdit||True if rows can be modified.|
|AllowNew||True if new rows can added|
|ApplyDefaultSort||True if the default sort order should be used.|
|Count||Returns the number of rows in this view|
|DataViewManager||The DataView associated with this view.|
|Item||Returns the Nth DataRow|
|RowFilter||An expression that determines which rows appear in this view|
|RowStateFilter||A DataViewRowState enumerated value that determines how rows are filtered according to their state. It can be None, CurrentRows, OriginalRows, ModifiedCurrent, ModifiedOriginal, Added, Deleted, Unchanged.|
|Sort||A string that specifies the column (or columns) used as sort keys.|
|Table||The source DataTable.|
|ToTable||(Added in 2.0) Allows you to create a new table based on data in the DataView.|
|AddNew||Adds a new row and returns a DatRowView object that can be used to set field values.|
|Delete||Deletes the row at the specified index.|
|Find||Returns the row index of a particular row in the DataView given the value of its key column(s). If more than one row matches then the first matching DataRow index is returned. If there are no matches then -1 is returned.|
|ListChanged||Fires when the list managed by the DataView changes, that is when an item is added, deleted, moved or modified.|
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