Gets the value of the selected item in the list control, or selects the item in the list control that contains the specified value.
<BrowsableAttribute(False)> _ <ThemeableAttribute(False)> _ <BindableAttribute(True, BindingDirection.TwoWay)> _ Public Overridable Property SelectedValue As String
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; }
[BrowsableAttribute(false)] [ThemeableAttribute(false)] [BindableAttribute(true, BindingDirection::TwoWay)] public: virtual property String^ SelectedValue { String^ get (); void set (String^ value); }
public function get SelectedValue () : String public function set SelectedValue (value : String)
<asp:ListControl SelectedValue="String" />
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.
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:
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"); }
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.
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.
<%@ 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"/> <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"/> <asp:Button ID="SelectButton" Text="Select Item" OnClick="Button_Click" runat="server"/> <br /><br /> <asp:Label ID="MessageLabel" runat="server"/> </form> </body> </html>
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