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ListControl.SelectedIndex Property

Gets or sets the lowest ordinal index of the selected items in the list.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

[ThemeableAttribute(false)] 
[BindableAttribute(true)] 
public virtual int SelectedIndex { get; set; }
/** @property */
public int get_SelectedIndex ()

/** @property */
public void set_SelectedIndex (int value)

public function get SelectedIndex () : int

public function set SelectedIndex (value : int)

Property Value

The lowest ordinal index of the selected items in the list. The default is -1, which indicates that nothing is selected.

Exception typeCondition

ArgumentOutOfRangeException

The index was set to less than -1, or greater than or equal to the number of items on the list at the time the list is rendered.

Use this property to determine the index of the currently selected item in the list if the list control allows only one selection. If the list control supports multiple selections, use this property to determine the lowest index of the selected items.

The value of the SelectedIndex property is not specifically saved on postback. It is restored on postback using the SelectedValue property. For example, if the SelectedValue property is 4, on postback, the SelectedIndex property is set to the index of the ListItem object that has a Value property of 4. If more than one ListItem object has a Value property of 4, the first item in the Items collection is selected.

This property cannot be set by themes or style sheet themes. For more information, see ThemeableAttribute and ASP.NET Themes and Skins Overview.

TopicLocation
How to: Determine the Selection in List Web Server ControlsBuilding ASP .NET Web Applications
How to: Determine the Selection in List Web Server ControlsBuilding ASP .NET Web Applications
How to: Set the Selection in List Web Server Controls (Visual Studio)Building ASP .NET Web Applications in Visual Studio

The following example demonstrates how to use SelectedIndex to determine the lowest index of the selected items in the CheckBoxList.

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
 
 <html>
 <script language="C#" runat="server">
 
    ICollection CreateDataSource() {
       DataTable dt = new DataTable();
       DataRow dr;
 
       dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
       dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
       dt.Columns.Add(new DataColumn("DateTimeValue", typeof(DateTime)));
       dt.Columns.Add(new DataColumn("BoolValue", typeof(bool)));
       dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double)));
 
       for (int i = 0; i < 9; i++) {
          dr = dt.NewRow();
 
          dr[0] = i;
          dr[1] = "Item " + i.ToString();
          dr[2] = DateTime.Now;
          dr[3] = (i % 2 != 0) ? true : false;
          dr[4] = 1.23 * (i+1);
 
          dt.Rows.Add(dr);
       }
 
       DataView dv = new DataView(dt);
       return dv;
    }
 
    void Page_Load(Object sender, EventArgs e) {
       if (!IsPostBack) {
          CheckBoxList1.DataSource = CreateDataSource();
          CheckBoxList1.DataTextField="StringValue";
          CheckBoxList1.DataValueField="CurrencyValue";
          CheckBoxList1.DataBind();
       }
    }
 
    void Index_Changed(Object sender, EventArgs e) {
 
       Label1.Text = "The index of the first item selected is: " + 
                     CheckBoxList1.SelectedIndex.ToString(); 
 
    }
 
 </script>
 
 <body>
 
    <form runat=server>
 
       <asp:CheckBoxList id="CheckBoxList1" 
            OnSelectedIndexChanged="Index_Changed"
            AutoPostBack="true"
            runat="server"/>
 
       <br>
 
       <asp:Label id="Label1" runat="server"/>
 
    </form>
 
 </body>
 </html>
 

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

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