ListControl.SelectedValue Property (System.Web.UI.WebControls)

SelectedValue Property

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

ListControl..::.SelectedValue Property

Gets the value of the selected item in the list control, or selects the item in the list control that contains the specified value.

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

Syntax

Visual Basic (Declaration)

<BrowsableAttribute(False)> _
<ThemeableAttribute(False)> _
<BindableAttribute(True, BindingDirection.TwoWay)> _
Public Overridable Property SelectedValue As String

Visual Basic (Usage)

Dim instance As ListControl
Dim value As String

value = instance.SelectedValue

instance.SelectedValue = value

[BrowsableAttribute(false)]
[ThemeableAttribute(false)]
[BindableAttribute(true, BindingDirection.TwoWay)]
public virtual string SelectedValue { get; set; }

Visual C++

[BrowsableAttribute(false)]
[ThemeableAttribute(false)]
[BindableAttribute(true, BindingDirection::TwoWay)]
public:
virtual property String^ SelectedValue {
    String^ get ();
    void set (String^ value);
}

JScript

public function get SelectedValue () : String
public function set SelectedValue (value : String)

ASP.NET

<asp:ListControl SelectedValue="String" />

Property Value

Type: System..::.String
The value of the selected item in the list control. The default is an empty string ("").

Exceptions

Exception	Condition
ArgumentOutOfRangeException	The selected value is not in the list of available values, and view state or other persistent state has been loaded (a postback has been performed). For more information, see the Remarks section in this topic.

Remarks

This property returns the Value property of the selected ListItem. The SelectedValue property is commonly used to determine the value of the selected item in the list control. If multiple items are selected, the value of the selected item with the lowest index is returned. If no item is selected, an empty string ("") is returned.

The SelectedValue property can also be used to select an item in the list control by setting it with the value of the item.

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

When the selected value is not in the list of available values and a postback is performed, an ArgumentOutOfRangeException is thrown. The following example shows how to catch an invalid value before postback happens:

Visual Basic

Me.DropDownList1.Items.Add(New ListItem( Text="Hello", Value="1" )) 
If DropDownList1.Items.FindByValue("2") IsNot Nothing Then 
    Response.Write("Found") 
End If

this.DropDownList1.Items.Add(new ListItem{ Text="Hello", Value="1" });
if(DropDownList1.Items.FindByValue("2") != null) {
    Response.Write("Found");
}

Examples

The following example demonstrates how to use the SelectedValue property to select an item in a ListBox control. Notice that this property can also be used to retrieve the value of the selected item.

Security Note:
This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  > 

<head runat="server">
    <title> ListControl SelectedValue Example </title>
<script runat="server">

      Sub Button_Click(sender As Object, e As EventArgs)

         ' Perform this operation in a try-catch block in case the item is not found.
         Try

            List.SelectedValue = ItemTextBox.Text
            MessageLabel.Text = "You selected " & List.SelectedValue + "."

         Catch ex As Exception

            List.SelectedValue = Nothing         
            MessageLabel.Text = "Item not found in ListBox control."

         End Try

      End Sub

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3> ListControl SelectedValue Example </h3>

      <asp:ListBox ID="List"
           runat="server">

         <asp:ListItem>Item 1</asp:ListItem>
         <asp:ListItem>Item 2</asp:ListItem>
         <asp:ListItem>Item 3</asp:ListItem>
         <asp:ListItem>Item 4</asp:ListItem>

      </asp:ListBox>

      <hr />

      Enter the value of the item to select: <br />
      <asp:TextBox ID="ItemTextBox"
           MaxLength="6"
           Text="Item 1"
           runat="server"/>

      &nbsp;&nbsp;

      <asp:Button ID="SelectButton"
           Text="Select Item"
           OnClick="Button_Click"
           runat="server"/>

      <br /><br />

      <asp:Label ID="MessageLabel"
           runat="server"/>     

   </form>

</body>
</html>

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  > 

<head runat="server">
    <title> ListControl SelectedValue Example </title>
<script runat="server">

      void Button_Click(Object sender, EventArgs e)
      {

         // Perform this operation in a try-catch block in case the item is not found.
         try
         {
            List.SelectedValue = ItemTextBox.Text;
            MessageLabel.Text = "You selected " + List.SelectedValue + ".";
         }
         catch (Exception ex)
         {
            List.SelectedValue = null;
            MessageLabel.Text = "Item not found in ListBox control.";
         }

      }

   </script>

</head>

<body>

   <form id="form1" runat="server">

      <h3> ListControl SelectedValue Example </h3>

      <asp:ListBox ID="List"
           runat="server">

         <asp:ListItem>Item 1</asp:ListItem>
         <asp:ListItem>Item 2</asp:ListItem>
         <asp:ListItem>Item 3</asp:ListItem>
         <asp:ListItem>Item 4</asp:ListItem>

      </asp:ListBox>

      <hr />

      Enter the value of the item to select: <br />
      <asp:TextBox ID="ItemTextBox"
           MaxLength="6"
           Text="Item 1"
           runat="server"/>

      &nbsp;&nbsp;

      <asp:Button ID="SelectButton"
           Text="Select Item"
           OnClick="Button_Click"
           runat="server"/>

      <br /><br />

      <asp:Label ID="MessageLabel"
           runat="server"/>     

   </form>

</body>
</html>

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1

Reference

ListControl Class

ListControl Members

System.Web.UI.WebControls Namespace

System..::.ArgumentOutOfRangeException