Bewerken

Share via

ListBox.SelectedIndex Property

  • Reference

Definition

Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms.dll

Gets or sets the zero-based index of the currently selected item in a ListBox.

public:
 virtual property int SelectedIndex { int get(); void set(int value); };
[System.ComponentModel.Bindable(true)]
[System.ComponentModel.Browsable(false)]
public override int SelectedIndex { get; set; }
[<System.ComponentModel.Bindable(true)>]
[<System.ComponentModel.Browsable(false)>]
member this.SelectedIndex : int with get, set
Public Overrides Property SelectedIndex As Integer

Property Value

Int32

A zero-based index of the currently selected item. A value of negative one (-1) is returned if no item is selected.

Attributes
BindableAttribute BrowsableAttribute

Exceptions

ArgumentOutOfRangeException

The assigned value is less than -1 or greater than or equal to the item count.

ArgumentException

The SelectionMode property is set to None.

Examples

The following code example demonstrates how to use the SelectedIndex property with the TopIndex property to move the currently selected item to the top of the list of items in the display area of the ListBox. The example further demonstrates how to remove items using the RemoveAt method of the System.Windows.Forms.ListBox.ObjectCollection class, and how to clear all item selection using the ClearSelected method. The code first moves the currently selected item in the ListBox to the top of the list. The code then removes all items before the currently selected item and clears all selections in the ListBox. This example requires that a ListBox containing items is added to a form and that an item is currently selected in the ListBox.

private:
   void RemoveTopItems()
   {
      // Determine if the currently selected item in the ListBox 
      // is the item displayed at the top in the ListBox.
      if ( listBox1->TopIndex != listBox1->SelectedIndex )

      // Make the currently selected item the top item in the ListBox.
      listBox1->TopIndex = listBox1->SelectedIndex;

      // Remove all items before the top item in the ListBox.
      for ( int x = (listBox1->SelectedIndex - 1); x >= 0; x-- )
      {
         listBox1->Items->RemoveAt( x );
      }

      // Clear all selections in the ListBox.
      listBox1->ClearSelected();
   }

private void RemoveTopItems()
{
   // Determine if the currently selected item in the ListBox 
   // is the item displayed at the top in the ListBox.
   if (listBox1.TopIndex != listBox1.SelectedIndex)
      // Make the currently selected item the top item in the ListBox.
      listBox1.TopIndex = listBox1.SelectedIndex;

   // Remove all items before the top item in the ListBox.
   for (int x = (listBox1.SelectedIndex -1); x >= 0; x--)
   {
      listBox1.Items.RemoveAt(x);
   }

   // Clear all selections in the ListBox.
   listBox1.ClearSelected();
}

Private Sub RemoveTopItems()
   ' Determine if the currently selected item in the ListBox 
   ' is the item displayed at the top in the ListBox.
   If listBox1.TopIndex <> listBox1.SelectedIndex Then
      ' Make the currently selected item the top item in the ListBox.
      listBox1.TopIndex = listBox1.SelectedIndex
   End If
   ' Remove all items before the top item in the ListBox.
   Dim x As Integer
   For x = listBox1.SelectedIndex - 1 To 0 Step -1
      listBox1.Items.RemoveAt(x)
   Next x

   ' Clear all selections in the ListBox.
   listBox1.ClearSelected()
End Sub

Remarks

For a standard ListBox, you can use this property to determine the index of the item that is selected in the ListBox. If the SelectionMode property of the ListBox is set to either SelectionMode.MultiSimple or SelectionMode.MultiExtended (which indicates a multiple-selection ListBox) and multiple items are selected in the list, this property can return the index to any selected item.

To retrieve a collection containing the indexes of all selected items in a multiple-selection ListBox, use the SelectedIndices property. If you want to obtain the item that is currently selected in the ListBox, use the SelectedItem property. In addition, you can use the SelectedItems property to obtain all the selected items in a multiple-selection ListBox.

Applies to

See also