ListBox.SelectedIndexChanged Event

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

ListBox.cs

Occurs when the SelectedIndex property or the SelectedIndices collection has changed.

public:
 event EventHandler ^ SelectedIndexChanged;

public event EventHandler? SelectedIndexChanged;

member this.SelectedIndexChanged : EventHandler 

Public Custom Event SelectedIndexChanged As EventHandler 

Event Type

EventHandler

Examples

The following code example demonstrates how to use the SelectedIndexChanged event to search for and select an item in a different ListBox control. The example uses the SelectedIndexChanged event to determine when the selected item in the ListBox is changed. The example code then reads the text of the item using the SelectedItem property and calls the FindString method on a different ListBox using the text returned by SelectedItem in the first ListBox. If an item is found in the other ListBox, the item is selected. This example requires that two ListBox controls, named listBox1 and listBox2, have been added to a form and that both ListBox controls contain items that are identical. The example also requires that the event-handling method defined in the example is connected to the SelectedIndexChanged event of listBox1.

private:
   void listBox1_SelectedIndexChanged( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Get the currently selected item in the ListBox.
      String^ curItem = listBox1->SelectedItem->ToString();

      // Find the string in ListBox2.
      int index = listBox2->FindString( curItem );

      // If the item was not found in ListBox 2 display a message box,
      //  otherwise select it in ListBox2.
      if ( index == -1 )
            MessageBox::Show( "Item is not available in ListBox2" );
      else
            listBox2->SetSelected( index, true );
   }

private void listBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
   // Get the currently selected item in the ListBox.
   string curItem = listBox1.SelectedItem.ToString();

   // Find the string in ListBox2.
   int index = listBox2.FindString(curItem);
   // If the item was not found in ListBox 2 display a message box, otherwise select it in ListBox2.
   if(index == -1)
      MessageBox.Show("Item is not available in ListBox2");
   else
      listBox2.SetSelected(index,true);
}

Private Sub listBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles listBox1.SelectedIndexChanged
   ' Get the currently selected item in the ListBox.
   Dim curItem As String = listBox1.SelectedItem.ToString()

   ' Find the string in ListBox2.
   Dim index As Integer = listBox2.FindString(curItem)
   ' If the item was not found in ListBox 2 display a message box, otherwise select it in ListBox2.
   If index = -1 Then
      MessageBox.Show("Item is not available in ListBox2")
   Else
      listBox2.SetSelected(index, True)
   End If
End Sub

Remarks

You can create an event handler for this event to determine when the selected index in the ListBox has been changed. This can be useful when you need to display information in other controls based on the current selection in the ListBox. You can use the event handler for this event to load the information in the other controls.

If the SelectionMode property is set to SelectionMode.MultiSimple or SelectionMode.MultiExtended, any change to the SelectedIndices collection, including removing an item from the selection, will raise this event.

For more information about handling events, see Handling and Raising Events.

See also

• SelectedIndex