HtmlSelect.RenderChildren(HtmlTextWriter) Methode

  • Referenz

Definition

Namespace:
System.Web.UI.HtmlControls
Assembly:
System.Web.dll

Rendert die untergeordneten Steuerelemente des HtmlSelect-Steuerelements in das angegebene HtmlTextWriter-Objekt.

protected:
 override void RenderChildren(System::Web::UI::HtmlTextWriter ^ writer);
protected public:
 override void RenderChildren(System::Web::UI::HtmlTextWriter ^ writer);
protected override void RenderChildren (System.Web.UI.HtmlTextWriter writer);
protected internal override void RenderChildren (System.Web.UI.HtmlTextWriter writer);
override this.RenderChildren : System.Web.UI.HtmlTextWriter -> unit
Protected Overrides Sub RenderChildren (writer As HtmlTextWriter)
Protected Friend Overrides Sub RenderChildren (writer As HtmlTextWriter)

Parameter

writer
HtmlTextWriter

Der HtmlTextWriter, der den gerenderten Inhalt empfängt.

Ausnahmen

HttpException

Es wurden mehrere Elemente ausgewählt, aber die Multiple-Eigenschaft wurde auf false festgelegt.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie sie die RenderChildren Methode außer Kraft setzen, sodass immer Standardoptionstext in einem benutzerdefinierten HtmlSelect Serversteuerelement angezeigt wird.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ 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>Custom HtmlSelect - RenderChildren - C# Example</title>
        <script runat="server">
      void HtmlInputButton1_ServerClick(Object sender, EventArgs e) 
      {
        if (HtmlSelect1.SelectedIndex >= 0)
        {
          if (HtmlSelect1.Multiple == true)
          {
            Div1.InnerHtml = "You selected:";
            for (int i=0; i<=HtmlSelect1.Items.Count - 1; i++)
            {
              if (HtmlSelect1.Items[i].Selected == true)
              {
                Div1.InnerHtml += "<br />    " + HtmlSelect1.Items[i].Value; 
              }     
            }
          }
          else
          {
            Div1.InnerHtml = "You selected " + HtmlSelect1.Value;
          }
        }
        else
        {
          Div1.InnerHtml = "You did not select an item.";
        }
      }
        </script>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom HtmlSelect - RenderChildren - C# Example</h3>
            
            <p>
      <aspSample:CustomHtmlSelectRenderChildren 
        id="HtmlSelect1"  multiple
        name="HtmlSelect1"
        runat="server">
        <option value="Option1">Option1</option>
        <option value="Option2">Option2</option>
        <option value="Option3">Option3</option>
      </aspSample:CustomHtmlSelectRenderChildren>
      </p>
      
      <p>
      <input 
        id="HtmlInputButton1" 
        runat="server" 
        type="button" 
        onserverclick="HtmlInputButton1_ServerClick"
        value="Select" 
        name="HtmlInputButton1" />  
      </p>
      
      <br />
      <div id="Div1" runat="server" 
        style="DISPLAY: inline; WIDTH: 256px; HEIGHT: 15px" />
       
        </form>
    </body>
</html>

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<%@ 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 xmlns="http://www.w3.org/1999/xhtml" >
    <head>
        <title>Custom HtmlSelect - RenderChildren - VB.NET Example</title>
        <script runat="server">
      Sub HtmlInputButton1_ServerClick(sender As Object, e As EventArgs)
        If HtmlSelect1.SelectedIndex >= 0 Then
            If HtmlSelect1.Multiple = True Then
              Div1.InnerHtml = "You selected:"
              Dim i As Integer
              For i = 0 To HtmlSelect1.Items.Count - 1
                  If HtmlSelect1.Items(i).Selected = True Then
                    Div1.InnerHtml += "<br />    " & HtmlSelect1.Items(i).Value
                  End If
              Next i
            Else
              Div1.InnerHtml = "You selected " & HtmlSelect1.Value
            End If
        Else
            Div1.InnerHtml = "You did not select an item."
        End If
      End Sub
        </script>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom HtmlSelect - RenderChildren - VB.NET Example</h3>
            
            <p>
      <aspSample:CustomHtmlSelectRenderChildren 
        id="HtmlSelect1"  multiple
        name="HtmlSelect1"
        runat="server">
        <option value="Option1">Option1</option>
        <option value="Option2">Option2</option>
        <option value="Option3">Option3</option>
      </aspSample:CustomHtmlSelectRenderChildren>
      </p>
      
      <p>
      <input 
        id="HtmlInputButton1" 
        runat="server" 
        type="button" 
        onserverclick="HtmlInputButton1_ServerClick"
        value="Select" 
        name="HtmlInputButton1" />  
      </p>
      
      <br />
      <div id="Div1" runat="server" 
        style="DISPLAY: inline; WIDTH: 256px; HEIGHT: 15px" />
       
        </form>
    </body>
</html>

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public sealed class CustomHtmlSelectRenderChildren : System.Web.UI.HtmlControls.HtmlSelect
    {
        protected override void RenderChildren(System.Web.UI.HtmlTextWriter writer)
        {
            // Create a default OPTION.
            System.Web.UI.WebControls.ListItem listItem = new System.Web.UI.WebControls.ListItem("<Select an option> ","");
            this.Items.Insert(0, listItem);
            
            // Call base's RenderChildren method.
            base.RenderChildren(writer);
        }
    }
}

<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomHtmlSelectRenderChildren
    Inherits System.Web.UI.HtmlControls.HtmlSelect

    Protected Overrides Sub RenderChildren(ByVal writer As System.Web.UI.HtmlTextWriter)

        ' Create a default OPTION.
        Dim listItem As New System.Web.UI.WebControls.ListItem("<Select an option> ", "")
        Me.Items.Insert(0, listItem)

        ' Call base's RenderChildren method.
        MyBase.RenderChildren(writer)
    End Sub
End Class

Hinweise

Die RenderChildren Methode überschreibt die Methode der Basisklasse, ohne die Basismethode aufzurufen RenderChildren . Jede der <option> Elemente zwischen den öffnenden und schließenden <select> Tags wird mit einem value Attribut gerendert, ein selected Attribut, wenn das Element ausgewählt ist, und dessen zugehöriger Text.

Wenn mehrere Elemente ausgewählt wurden, die Multiple Eigenschaft jedoch auf false"Festgelegt" festgelegt ist, wird eine HttpException Ausnahme ausgelöst.

Gilt für

Siehe auch