HtmlSelect.RenderChildren(HtmlTextWriter) Method
Definition
Important
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Renders the HtmlSelect control's child controls to the specified HtmlTextWriter object.
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 -> unitProtected Overrides Sub RenderChildren (writer As HtmlTextWriter)Protected Friend Overrides Sub RenderChildren (writer As HtmlTextWriter)Parameters
- writer
- HtmlTextWriter
The HtmlTextWriter that receives the rendered content.
Exceptions
Multiple items were selected but the Multiple property is set to false.
Examples
The following code example demonstrates how to override the RenderChildren method so that it always displays default option text in a custom HtmlSelect server control.
<%@ 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
Remarks
The RenderChildren method overrides the base class's RenderChildren method without calling the base method. Each of the <option> elements between the opening and closing <select> tags is rendered with a value attribute, a selected attribute if the item is selected, and its associated text.
If multiple items were selected but the Multiple property is set to false, then an HttpException exception is thrown.
