ListItem.Value 屬性

  • 參考

定義

命名空間:
System.Web.UI.WebControls
組件:
System.Web.dll

取得或設定與 ListItem 關聯的值。

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

屬性值

String

與 ListItem 關聯的值。 預設為 Empty。

範例

注意

下列程式碼範例會使用單一檔案程式碼模型，如果直接複製到程式碼後置檔案，可能無法正常運作。 此程式碼範例必須複製到副檔名為 .aspx 的空白文字檔中。 如需Web Form程式碼模型的詳細資訊，請參閱ASP.NET Web Forms頁碼模型。

<!-- 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>

備註

Value使用 屬性來指定或判斷與 ListItem 相關聯的值。

注意

Value如果屬性包含 null ，存取 get 子會傳回 屬性的值 Text 。 Text如果屬性接著包含 null ， String.Empty 則會傳回 。

當設定時，此屬性的值可以使用設計工具自動儲存到資源檔。 如需詳細資訊，請參閱 LocalizableAttribute和全球化和當地語系化。

適用於

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