ComboBox (cbo)

alt textCombobox - Allows the user to either select an item from a drop-down box or enter a different item.

Both the ComboBox and ListBox controls are derived from the ListControl class



Examples

alt text

Adding to single column

this.ComboBox1.Items.Add "Item 1"; 
this.ComboBox1.Items.Add "Item 2";
this.ComboBox1.SelectedIndex = 0;

Currently selected item

Obtaining the currently selected item in a combo box.

System.Windows.Forms.MessageBox.Show(this.cboComboBox1.Value) ; 

Select a value

You can use FindString to return the index of the first item that starts with a specified string.

this.cboComboBox1.Text = "Item 2"; 
this.cboComboBox1.SelectedIndex = this.cboComboBox1.FindString("Item 1");

Check if a value has been chosen

if (this.cboMyComboBox.SelectedItem == null) 
{}

DataSource

objDataTable = new System.Data.DataTable; 
objDataTable.TableName = "Applications";
objDataTable.Columns.Add("ArticleApplication", GetType(System.String));
foreach (objDataRow in clsDatabase.mobjDataSet.Tables("ApplicationNames").Rows)
{
   objDataRowNew = objDataTable.NewRow();
   objDataRowNew("ArticleApplication") = objDataRow("ArticleApplication");
   objDataTable.Rows.Add(objDataRowNew);
}
this.cboComboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
this.cboComboBox1.DataSource = objDataTable;
this.cboComboBox1.DisplayMember = "ArticleApplication";


Properties

AllowSelection Gets a value indicating whether the list enables selection of list items. (Inherited from ListControl.)
AutoCompleteMode (Added in 2.0) Gets or sets an option that controls how automatic completion works for the ComboBox.
AutoCompleteSource Gets or sets a value specifying the source of complete strings used for automatic completion.
DataManager Gets the CurrencyManager associated with this control. (Inherited from ListControl.)
DataSourceGets or sets the data source for this ComboBox.
DisplayMember Gets or sets the property to display for this ListControl. (Inherited from ListControl.)
DropDownHeightGets or sets the height in pixels of the drop-down portion of the ComboBox.
DropDownStyleGets or sets a value specifying the style of the combo box.
DropDownWidth Gets or sets the width of the of the drop-down portion of a combo box.
DroppedDown Gets or sets a value indicating whether the combo box is displaying its drop-down portion.
FlatStyle Gets or sets the appearance of the ComboBox.
Focused Overridden. Gets a value indicating whether the ComboBox has focus.
FormatString Gets or sets the format-specifier characters that indicate how a value is to be displayed. (Inherited from ListControl.)
FormattingEnabled Gets or sets a value indicating whether formatting is applied to the DisplayMember property of the ListControl. (Inherited from ListControl.)
IntegralHeight Gets or sets a value indicating whether the control should resize to avoid showing partial items.
ItemHeightGets or sets the height of an item in the combo box.
Items Gets an object representing the collection of the items contained in this ComboBox.
MaxDropDownItemsGets or sets the maximum number of items to be shown in the drop-down portion of the ComboBox.
MaxLengthGets or sets the number of characters a user can type into the ComboBox.
PreferredHeight Gets the preferred height of the ComboBox.
SelectedIndexSets the index specifying the currently selected item. Problems when populating before control is displayed. Overridden.
SelectedItem Sets the currently selected item in the ComboBox. There is no selection when the focus is taken away from the combobox. For example when you press a button nothing will be selected.
SelectedText Sets the text that is currently selected in the editable portion of a ComboBox. There is no selection when the focus is taken away from the combobox. For example when you press a button nothing will be selected.
SelectedValueSets the value of the member property specified by the ValueMember property. Problems when populating before control is displayed.
SelectionLength Gets or sets the number of characters selected in the editable portion of the combo box.
SelectionStart Gets or sets the starting index of text selected in the combo box.
SortedGets or sets a value indicating whether the items in the combo box are sorted.
TextOverridden. Gets or sets the text associated with this control.
ValueMemberGets or sets the property to use as the actual value for the items in the ListControl. (Inherited from ListControl.)

Methods

AddAdds an item to the list of items
AddRangeAdds an array of items to the list of items
AddItemsCore Adds the specified items to the combo box.
BeginUpdate Maintains performance when items are added to the ComboBox one at a time.
Dispose Overloaded. Releases the resources used by the ComboBox.
EndUpdate Resumes painting the ComboBox control after painting is suspended by the BeginUpdate method.
FilterItemOnProperty Overloaded. Returns the current value of the ListControl item, if the item is a property of an instance of the ListControl class. (Inherited from ListControl.)
FindString Overloaded. Finds the first item in the ComboBox that starts with the specified string.
FindStringExact Overloaded. Finds the item that exactly matches the specified string.
GetItemHeight Returns the height of an item in the ComboBox.
GetItemText Returns the text representation of the specified item. (Inherited from ListControl.)
OnClick Raises the Click event. (Inherited from Control.)
RefreshItem Overridden. Refreshes the item contained at the specified location.
RefreshItemsOverridden. Refreshes all ComboBox items.
ResetText Overridden.
Select Overloaded.
SelectAll Selects all the text in the editable portion of the ComboBox.
SetBoundsCore Overridden. Sets the size and location of the ComboBox.
ToString Overridden. Returns a string that represents the ComboBox control.

Events

BackgroundImageChanged Occurs when the value of the BackgroundImage property changes.
BackgroundImageLayoutChanged Occurs when the BackgroundImageLayout property changes.
DrawItem Occurs when a visual aspect of an owner-drawn ComboBox changes.
DropDown Occurs when the drop-down portion of a ComboBox is shown.
DropDownClosed Occurs when the drop-down portion of the ComboBox is no longer visible.
DropDownStyleChanged Occurs when the DropDownStyle property has changed.
Format Occurs when the control is bound to a data value. (Inherited from ListControl.)
FormatInfoChanged Occurs when the value of the FormatInfo property changes. (Inherited from ListControl.)
FormatStringChanged Occurs when value of the FormatString property changes (Inherited from ListControl.)
FormattingEnabledChanged Occurs when the value of the FormattingEnabled property changes. (Inherited from ListControl.)
MeasureItem Occurs each time an owner-drawn ComboBox item needs to be drawn and when the sizes of the list items are determined.
SelectedIndexChangedOccurs when the SelectedIndex property has changed.
SelectedValueChanged Occurs when the SelectedValue property changes. (Inherited from ListControl.)
SelectionChangeCommittedOccurs when the selected item has changed and that change is displayed in the ComboBox.
TextUpdate Occurs when the control has formatted the text, but before the text is displayed.
ValueMemberChanged Occurs when the ValueMember property changes. (Inherited from ListControl.)

private void cboComboBox1_SelectedIndexChanged(object sender, System.EventArgs e) 
{
   ComboBox myCombo;
   myComboBox = (ComboBox)sender;
   myComboBox = this.cboComboBox1;

   string theValue = (string)myCombo.SelectedItem;
}

public partial class Form1 : Form 
{
    public Form1()
    {
        InitializeComponent();

        this.comboBox1.ValueMember = "Property_DayID";
        this.comboBox1.DisplayMember = "Property_DayDisplayName";

        DayDisplayName oDay;
        oDay = new DayDisplayName("1", "Mon", "Monday");
        this.comboBox1.Items.Add(oDay);

        oDay = new DayDisplayName("2", "Tue", "Tuesday");
        this.comboBox1.Items.Add(oDay);

        oDay = new DayDisplayName("3", "Wed", "Wednesday");
        this.comboBox1.Items.Add(oDay);
        //this.comboBox1.Items.Add("Wednesday");

        this.comboBox1.Text = "Tuesday";
        //this.comboBox1.SelectedIndex = this.comboBox1.FindString("Tuesday");

    }
    private void btnComboBox_GetValue_Click(object sender, EventArgs e)
    {
        string selectedvalue;
        selectedvalue = this.comboBox1.Text;

        System.Windows.Forms.MessageBox.Show(selectedvalue);
    }
}

public class DayDisplayName
{
    public string Property_DayID { get; set; }
    public string Property_DayName { get; set; }
    public string Property_DayDisplayName { get; set; }

    public DayDisplayName(
        string property_DayID,
        string property_DayName,
        string property_DayDisplayName)
    {
        this.Property_DayID = property_DayID;
        this.Property_DayName = property_DayName;
        this.Property_DayDisplayName = property_DayDisplayName;
    }
}


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