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ListItem-Konstruktor ()

  • Artikel

Initialisiert eine neue Instanz der ListItem-Klasse.

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

Syntax

'Declaration
Public Sub New
'Usage
Dim instance As New ListItem

public ListItem ()

public:
ListItem ()

public ListItem ()

public function ListItem ()

Hinweise

Mit diesem Konstruktor können Sie unter Verwendung von Standardwerten eine neue Instanz der ListItem-Klasse erstellen und initialisieren.

In der folgenden Tabelle sind die anfänglichen Eigenschaftenwerte für eine Instanz von ListItem aufgeführt.

Eigenschaft

Anfangswert

Text

NULL (Nothing in Visual Basic)

Value

NULL (Nothing in Visual Basic)

Enabled

true

Beispiel

Hinweis

Im folgenden Codebeispiel wird das Einzeldatei-Codemodell verwendet. Das Beispiel funktioniert möglicherweise nicht, wenn es direkt in eine CodeBehind-Datei kopiert wird. Dieses Codebeispiel muss in eine leere Textdatei mit einer ASPX-Erweiterung kopiert werden. Weitere Informationen zum Web Forms-Codemodell finden Sie unter Codemodell für ASP.NET-Webseiten.

<%@ 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. -->

<html>
 <head>
 
     <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>
     <p>
     <form 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>
          

<!-- 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" %>
<html>
 <head>
 
     <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>
     <p>
     <form 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>
          

<!-- 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="JScript" %>
<html>
 <head>
 
     <script language="JScript" runat="server">
 
         function AddBtn_Click(Sender : Object, e : EventArgs) 
         {
             if (ListBox1.SelectedIndex > -1) 
             {
                 if (ListBox2.Items.FindByValue(ListBox1.SelectedItem.Text)==null) 
                 {
                     var Item : ListItem = new ListItem();
                     // Text and Value are swapped.
                     Item.Text = ListBox1.SelectedItem.Value;
                     Item.Value = ListBox1.SelectedItem.Text;
                     ListBox2.Items.Add(Item);
                 }
             }
         }
 
         function DelBtn_Click(Sender : Object, e : EventArgs) 
         {
             if (ListBox2.SelectedIndex > -1) 
             {
                 ListBox2.Items.Remove(ListBox2.SelectedItem);
             }
         }
 
     </script>
 
 </head>
 <body>
 
     <h3>ListItem Example</h3>
     <p>
     <form 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>

Plattformen

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

Siehe auch

Referenz

ListItem-Klasse
ListItem-Member
System.Web.UI.WebControls-Namespace
ListControl-Klasse
RadioButtonList
ListBox-Klasse
DropDownList-Klasse
CheckBoxList-Klasse

Weitere Ressourcen

ListBox-Webserver-Steuerelement
Übersicht über die RadioButton- und RadioButtonList-Webserversteuerelemente
BulletedList-Webserver-Steuerelement
DropDownList-Webserversteuerelement