HtmlSelect.RenderChildren(HtmlTextWriter) 方法

定義

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

將 HtmlSelect 控制項的子控制項渲染成指定的 HtmlTextWriter 物件。

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)

參數

writer
HtmlTextWriter

HtmlTextWriter那個接收渲染內容的裝置。

例外狀況

HttpException

選取了多個項目，但 Multiple 屬性設定為 false。

範例

以下程式碼範例示範如何覆寫該 RenderChildren 方法，使其在自訂 HtmlSelect 伺服器控制項中始終顯示預設選項文字。

<%@ 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

備註

該 RenderChildren 方法會覆寫基底類別的方法 RenderChildren ，但不會呼叫基底方法。 開頭與結束<select>標籤之間的每個<option>元素都會以屬性、若選取項目則為selected屬性，以及相關文字來呈現value。

若選取多個項目但 Multiple 屬性設為 false，則 HttpException 會拋出例外。

適用於

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