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ValidationSummary.OnPreRender(EventArgs) Method

  • Reference

Definition

Namespace:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Raises the PreRender event.

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)

Parameters

e
EventArgs

An EventArgs that contains the event data.

Examples

The following code example demonstrates how to override the OnPreRender method so that it always displays error messages as bold in a custom ValidationSummary server control.

Important

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

<%@ 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 ValidationSummary - AddAttributesToRender - C# Example</title>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom ValidationSummary - AddAttributesToRender - C# Example</h3>

      <table id="Table1" cellpadding="4" cellspacing="0">
        <tr>
          <td>
            <table id="Table2" cellpadding="4" cellspacing="0"
             style="background-color:#eeeeee;">
              <tr>
                <td colspan="3"><b>Credit Card Information</b> </td>
              </tr>
              <tr>
                <td align="right">Card Type: </td>
                <td>
                  <asp:RadioButtonList id="RadioButtonList1" runat="server" RepeatLayout="Flow">
                      <asp:ListItem>MasterCard</asp:ListItem>
                      <asp:ListItem>Visa</asp:ListItem>
                  </asp:RadioButtonList>
                </td>
                <td align="center" rowspan="1">
                  <asp:RequiredFieldValidator 
                    id="RequiredFieldValidator1" 
                    runat="server" 
                    ErrorMessage="Card Type" 
                    Width="100%" 
                    Display="Static" 
                    ControlToValidate="RadioButtonList1">*
                  </asp:RequiredFieldValidator>
                </td>
              </tr>
              <tr>
                <td align="right">Card Number: </td>
                <td><asp:TextBox id="TextBox1" runat="server"></asp:TextBox></td>
                <td>
                  <asp:RequiredFieldValidator 
                    id="RequiredFieldValidator2" 
                    runat="server" 
                    ErrorMessage="Card Number" 
                    Width="100%" 
                    Display="Static" 
                    ControlToValidate="TextBox1">*
                  </asp:RequiredFieldValidator>
                </td>
              </tr>
              <tr>
                <td></td>
                <td><asp:Button id="Button1" runat="server" text="Validate"></asp:Button></td>
                <td></td>
              </tr>
            </table>
          </td>
        </tr>
        <tr>
          <td valign="top">
            <aspSample:CustomValidationSummaryAddAttributesToRender
              id="ValidationSummary1" 
              runat="server" 
              DisplayMode="BulletList" 
              HeaderText="You must enter a value in the following fields:" />
          </td>
        </tr>
      </table>

        </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 ValidationSummary - AddAttributesToRender - VB.NET Example</title>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom ValidationSummary - AddAttributesToRender - VB.NET Example</h3>


                <table id="Table1" cellpadding="4" cellspacing="0">
                    <tr>
                        <td>
                            <table id="Table2" cellpadding="4" cellspacing="0" style="background-color:#eeeeee">
                                <tr>
                                    <td colspan="3"><b>Credit Card Information</b> </td>
                                </tr>
                                <tr>
                                    <td align="right">Card Type: </td>
                                    <td><asp:RadioButtonList id="RadioButtonList1" runat="server" RepeatLayout="Flow">
                                            <asp:ListItem>MasterCard</asp:ListItem>
                                            <asp:ListItem>Visa</asp:ListItem>
                                        </asp:RadioButtonList>
                                    </td>
                                    <td align="center" rowspan="1">
                                        <asp:RequiredFieldValidator id="RequiredFieldValidator1" 
                                         runat="server" ErrorMessage="Card Type. " Width="100%" 
                                         Display="Static" ControlToValidate="RadioButtonList1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="right">Card Number: </td>
                                    <td><asp:TextBox id="TextBox1" runat="server"></asp:TextBox></td>
                                    <td>
                                        <asp:RequiredFieldValidator id="RequiredFieldValidator2" 
                                         runat="server" ErrorMessage="Card Number. " Width="100%" 
                                         Display="Static" ControlToValidate="TextBox1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td></td>
                                    <td><asp:Button id="Button1" runat="server" text="Validate"></asp:Button></td>
                                    <td></td>
                                </tr>
                            </table>
                        </td>
                        <td valign="top">
                            <table id="Table3" cellpadding="4" cellspacing="0" >
                                <tr>
                                    <td><aspSample:CustomValidationSummaryAddAttributesToRender
                                        id="ValidationSummary1" runat="server" DisplayMode="BulletList"
                                        HeaderText="You must enter a value in the following fields:" />
                                    </td>
                                </tr>
                            </table>
                        </td>
                     </tr>
                </table>

        </form>
    </body>
</html>

using System.Web;
using System.Security.Permissions;

namespace Samples.AspNet.CS.Controls
{
  [AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
  public sealed class CustomValidationSummaryAddAttributesToRender : System.Web.UI.WebControls.ValidationSummary
  {
    protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
    {
      // Show the error message as bold.
      writer.AddStyleAttribute(System.Web.UI.HtmlTextWriterStyle.FontWeight, "bold");
      
      // Call the Base's AddAttributesToRender method.
      base.AddAttributesToRender(writer);
    }
  }
}

Imports System.Web
Imports System.Security.Permissions

Namespace Samples.AspNet.VB.Controls
    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public NotInheritable Class CustomValidationSummaryAddAttributesToRender
        Inherits System.Web.UI.WebControls.ValidationSummary

        Protected Overrides Sub AddAttributesToRender(ByVal writer As System.Web.UI.HtmlTextWriter)

            ' Show the error message as bold.
            writer.AddStyleAttribute(System.Web.UI.HtmlTextWriterStyle.FontWeight, "bold")

            ' Call the Base's AddAttributesToRender method.
            MyBase.AddAttributesToRender(writer)
        End Sub
    End Class
End Namespace

Applies to