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ListBox.SelectedIndex Property

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

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

[BindableAttribute(true)]
[BrowsableAttribute(false)]
public override int SelectedIndex { get; set; }

Property Value

Type: System.Int32
A zero-based index of the currently selected item. A value of negative one (-1) is returned if no item is selected.

ExceptionCondition
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.

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.

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();
}

.NET Framework

Supported in: 4.6, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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