ListItem.Value 属性

  • 参考

定义

命名空间:
System.Web.UI.WebControls
程序集:
System.Web.dll

获取或设置与 ListItem 关联的值。

public:
 property System::String ^ Value { System::String ^ get(); void set(System::String ^ value); };
public string Value { get; set; }
member this.Value : string with get, set
Public Property Value As String

属性值

String

与 ListItem 关联的值。 默认值为 Empty。

示例

备注

下面的代码示例使用单文件代码模型，如果直接复制到代码隐藏文件中，可能无法正常工作。 必须将此代码示例复制到扩展名为 .aspx 的空文本文件中。 有关Web Forms代码模型的详细信息，请参阅 ASP.NET Web Forms页代码模型。

<!-- The following example demonstrates adding items to and removing items
from ListBox controls. When an item is selected in ListBox1, a new ListBoxItem with
the same value can be created and added to ListBox2, if ListBox2 does not already 
contain an item with that value. When the new ListBoxItem is created, it receives 
the Value property of the selected item as its Text property, and the Text property
of the selected item as its value property. -->

<%@ 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 xmlns="http://www.w3.org/1999/xhtml" >
 <head>
    <title>ListItem Example</title>
<script runat="server">
 
         void AddBtn_Click(Object Sender, EventArgs e) 
         {
             if (ListBox1.SelectedIndex > -1) 
             {
                  if (ListBox2.Items.FindByValue(ListBox1.SelectedItem.Text) == null) 
                 {
                      ListItem Item = new ListItem();
                      // Text and Value are swapped.
                     Item.Text = ListBox1.SelectedItem.Value;
                     Item.Value = ListBox1.SelectedItem.Text;
                     ListBox2.Items.Add(Item);
                  }
             }
         }
 
         void DelBtn_Click(Object Sender, EventArgs e) 
         {
             if (ListBox2.SelectedIndex > -1) 
             {
                 ListBox2.Items.Remove(ListBox2.SelectedItem);
             }
         }
 
     </script>
 
 </head>
 <body>
 
     <h3>ListItem Example</h3>
     <form id="form1" runat="server">
     <table>
     <tr><td>
         <asp:ListBox id="ListBox1" Width="100px" runat="server">
             <asp:ListItem Value="Value 1">Item 1</asp:ListItem>
             <asp:ListItem Value="Value 2">Item 2</asp:ListItem>
             <asp:ListItem Value="Value 3">Item 3</asp:ListItem>
             <asp:ListItem Value="Value 4">Item 4</asp:ListItem>
             <asp:ListItem Value="Value 5" Selected="True">Item 5</asp:ListItem>
             <asp:ListItem Value="Value 6">Item 6</asp:ListItem>
         </asp:ListBox>
     </td><td>
         <asp:button Text="--->" OnClick="AddBtn_Click" runat="server" /><br />
         <asp:button Text="<---" OnClick="DelBtn_Click" runat="server" />
    </td><td>
         <asp:ListBox id="ListBox2" Width="100px" runat="server"/>
     </td></tr>
     </table>
     </form>
 
 </body>
 </html>

<%@ Page Language="VB" %>
<!-- The following example demonstrates adding items to and removing items
from ListBox controls. When an item is selected in ListBox1, a new ListBoxItem with
the same value can be created and added to ListBox2, if ListBox2 does not already 
contain an item with that value. When the new ListBoxItem is created, it receives 
the Value property of the selected item as its Text property, and the Text property
of the selected item as its value property. -->

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
 <head>
    <title>ListItem Example</title>
<script language="VB" runat="server">
 
         Sub AddBtn_Click(Sender As Object, e As EventArgs)
             If ListBox1.SelectedIndex > -1 Then
                  If ListBox2.Items.FindByValue(ListBox1.SelectedItem.Text) is Nothing Then
                      Dim Item As ListItem = new ListItem()
                      'Text and Value are swapped
                     Item.Text = ListBox1.SelectedItem.Value
                     Item.Value = ListBox1.SelectedItem.Text
                     ListBox2.Items.Add(Item)
                  End If
             End If
         End Sub
 
         Sub DelBtn_Click(Sender As Object, e As EventArgs)
             If ListBox2.SelectedIndex > -1 Then
                 ListBox2.Items.Remove(ListBox2.SelectedItem)
             End If
         End Sub
 
     </script>
 
 </head>
 <body>
 
     <h3>ListItem Example</h3>
     <form id="form1" runat="server">
     <table>
     <tr><td>
         <asp:ListBox id="ListBox1" Width="100px" runat="server">
             <asp:ListItem Value="Value 1">Item 1</asp:ListItem>
             <asp:ListItem Value="Value 2">Item 2</asp:ListItem>
             <asp:ListItem Value="Value 3">Item 3</asp:ListItem>
             <asp:ListItem Value="Value 4">Item 4</asp:ListItem>
             <asp:ListItem Value="Value 5" Selected="True">Item 5</asp:ListItem>
             <asp:ListItem Value="Value 6">Item 6</asp:ListItem>
         </asp:ListBox>
     </td><td>
         <asp:button Text="--->" OnClick="AddBtn_Click" runat="server" /><br />
         <asp:button Text="<---" OnClick="DelBtn_Click" runat="server" />
    </td><td>
         <asp:ListBox id="ListBox2" Width="100px" runat="server"/>
     </td></tr>
     </table>
     </form>
 
 </body>
 </html>

注解

Value使用 属性指定或确定与 ListItem关联的值。

备注

Value如果 属性包含 null，则get访问器返回 属性的值Text。 Text如果 属性又包含 null，String.Empty则返回 。

设置此属性的值时，可以使用设计器工具自动保存到资源文件。 有关详细信息，请参阅 LocalizableAttribute 和 全球化和本地化。

适用于

另请参阅