HtmlSelect.RenderChildren(HtmlTextWriter) Método
Definição
Importante
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Renderiza os controles filho do controle HtmlSelect no objeto HtmlTextWriter especificado.
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)Parâmetros
- writer
- HtmlTextWriter
O HtmlTextWriter que recebe o conteúdo renderizado.
Exceções
Foram selecionados vários itens, mas a propriedade Multiple está definida para false.
Exemplos
O exemplo de código a seguir demonstra como substituir o RenderChildren método para que ele sempre exiba o texto de opção padrão em um controle de servidor personalizado HtmlSelect .
<%@ 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
Comentários
O RenderChildren método substitui o método da RenderChildren classe base sem chamar o método base. Cada um dos <option> elementos entre as marcas de abertura e fechamento <select> é renderizado com um value atributo, um selected atributo se o item for selecionado e seu texto associado.
Se vários itens foram selecionados, mas a Multiple propriedade está definida como false, uma exceção HttpException será lançada.