RequiredFieldValidator.EvaluateIsValid Method

Called during the validation stage when ASP.NET processes a Web Form.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

protected:
virtual bool EvaluateIsValid () override
protected boolean EvaluateIsValid ()
protected override function EvaluateIsValid () : boolean
Not applicable.

Return Value

true if the value in the input control is valid; otherwise, false.

The following code example demonstrates how to override the EvaluateIsValid method in a custom server control so that it always returns false if the value of the RequiredFieldValidator is null or empty, and always returns true otherwise.

No code example is currently available or this language may not be supported.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL.Controls" Assembly="Samples.AspNet.JSL" %>
<%@ Page Language="VJ#" 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 RequiredFieldValidator - EvaluateIsValid - VJ# Example</title>
    <script runat="server">
        void Button1_Click(Object sender, EventArgs e) 
        {
            if (get_Page().get_IsValid()) {
                Label1.set_Text("Required field is filled!");
            }
            else {
                Label1.set_Text("Required field is empty!");
            }
        } //Button1_Click
    </script>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">
      <h3>Custom RequiredFieldValidator - EvaluateIsValid - VJ# Example</h3>

      <table border="0" cellpadding="4" cellspacing="0">
        <tr valign="top">
          <td colspan="3">
            <asp:Label ID="Label1" runat="server" Text="Fill in the required field below" />
          </td>
        </tr>
        <tr>
          <td align="right">Card Number:</td>
          <td>
            <asp:TextBox id="TextBox1" runat="server" />
          </td>
          <td>
            <aspSample:CustomRequiredFieldValidatorEvaluateIsValid 
              id="RequiredFieldValidator1" 
              runat="server" 
              ControlToValidate="TextBox1" 
              Display="Static" 
              ErrorMessage="*" />
          </td>
        </tr>
        <tr>
          <td>&nbsp;</td>
          <td>
            <asp:Button 
              id="Button1" 
              runat="server" 
              Text="Validate" 
              OnClick="Button1_Click" />
          </td>
          <td>&nbsp;</td>
        </tr>
      </table>

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

	...

package Samples.AspNet.JSL.Controls;

public class CustomRequiredFieldValidatorEvaluateIsValid
    extends System.Web.UI.WebControls.RequiredFieldValidator
{
    protected boolean EvaluateIsValid()
    {
        // Get the ControlToValidate's value.
        String controlValue = GetControlValidationValue(get_ControlToValidate());
        // If ControlToValidate's value is null or empty, then return false.
        if (controlValue == null || controlValue.Trim().Equals("")) {
            return false;
        }
        // Else the control contains a value so return true.
        else {
            return true;
        }
    } //EvaluateIsValid
} //CustomRequiredFieldValidatorEvaluateIsValid

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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