HtmlSelect.OnPreRender Method (EventArgs)
.NET Framework (current version)
Raises the PreRender event for the HtmlSelect control.
Assembly: System.Web (in System.Web.dll)
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.
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>
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; } } }
.NET Framework
Available since 1.1
Available since 1.1
Show: