ListItem.Value 屬性
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
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
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
另請參閱
意見反應
https://aka.ms/ContentUserFeedback。
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