HtmlSelect.RenderChildren(HtmlTextWriter) Metod

Definition

Namnområde:: System.Web.UI.HtmlControls

Sammansättning:: System.Web.dll

Viktigt

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Renderar kontrollens HtmlSelect underordnade kontroller till det angivna HtmlTextWriter objektet.

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)

Parametrar

writer: HtmlTextWriter

Det HtmlTextWriter som tar emot det renderade innehållet.

Undantag

HttpException

Flera objekt har markerats men egenskapen Multiple är inställd på false.

Exempel

Följande kodexempel visar hur du åsidosätter RenderChildren metoden så att den alltid visar standardalternativtext i en anpassad HtmlSelect serverkontroll.

<%@ 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)
          {
            Div1.InnerHtml = "You selected:";
            for (int i=0; i<=HtmlSelect1.Items.Count - 1; i++)
            {
              if (HtmlSelect1.Items[i].Selected)
              {
                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

Kommentarer

Metoden RenderChildren åsidosätter basklassens RenderChildren metod utan att anropa basmetoden. Vart och ett av elementen <option> mellan de inledande och avslutande <select> taggarna återges med ett value attribut, ett selected attribut om objektet är markerat och dess associerade text.

Om flera objekt har valts men egenskapen Multiple har angetts till falsegenereras ett HttpException undantag.

Gäller för

Se även

ListItem

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