HtmlSelect.OnPreRender(EventArgs) Método
Definição
Aciona o evento PreRender do controle HtmlSelect.Raises the PreRender event for the HtmlSelect control.
protected:
override void OnPreRender(EventArgs ^ e);
protected public:
override void OnPreRender(EventArgs ^ e);
protected override void OnPreRender (EventArgs e);
protected internal override void OnPreRender (EventArgs e);
override this.OnPreRender : EventArgs -> unit
Protected Overrides Sub OnPreRender (e As EventArgs)
Protected Friend Overrides Sub OnPreRender (e As EventArgs)
Parâmetros
Exemplos
O exemplo de código a seguir demonstra como substituir o OnPreRender método para que ele permita várias seleções em um HtmlSelect controle de servidor personalizado.The following code example demonstrates how to override the OnPreRender method so that it allows multiple selections 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 - OnPreRender - 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 - OnPreRender - C# Example</h3>
<p>
<aspSample:CustomHtmlSelectOnPreRender
id="HtmlSelect1"
name="HtmlSelect1"
runat="server">
<option value="Option1">Option1</option>
<option value="Option2">Option2</option>
<option value="Option3">Option3</option>
</aspSample:CustomHtmlSelectOnPreRender>
</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 - OnPreRender - 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 - OnPreRender - VB.NET Example</h3>
<p>
<aspSample:CustomHtmlSelectOnPreRender
id="HtmlSelect1"
name="HtmlSelect1"
runat="server">
<option value="Option1">Option1</option>
<option value="Option2">Option2</option>
<option value="Option3">Option3</option>
</aspSample:CustomHtmlSelectOnPreRender>
</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 CustomHtmlSelectOnPreRender : System.Web.UI.HtmlControls.HtmlSelect
{
protected override void OnPreRender(System.EventArgs e)
{
// Call the base's OnPreRender method.
base.OnPreRender(e);
// Allow multiple selections.
this.Multiple = true;
}
}
}
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomHtmlSelectOnPreRender
Inherits System.Web.UI.HtmlControls.HtmlSelect
Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)
' Call the base's OnPreRender method.
MyBase.OnPreRender(e)
' Allow multiple selections.
Me.Multiple = True
End Sub
End Class
Comentários
Se a Size propriedade for maior que 1, o OnPreRender método registrará o HtmlSelect controle com o Page controle como um que exija o processamento de postback.If the Size property is greater than 1, then the OnPreRender method registers the HtmlSelect control with the Page control as one that requires postback processing.