RegularExpressionValidator.EvaluateIsValid Method

Indicates whether the value in the input control is valid.

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 checks the value against the expression for a match in a RegularExpressionValidator.

Security noteSecurity Note:

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 (Visual Studio).

No code example is currently available or this language may not be supported.
package Samples.AspNet.JSL.Controls; 

public class CustomRegularExpressionValidatorEvaluateIsValid
    extends System.Web.UI.WebControls.RegularExpressionValidator
{
    protected boolean EvaluateIsValid()
    {
        // Get the control to validate's validation value
        String controlValue = GetControlValidationValue(this.
            get_ControlToValidate());
        // If the value is null or empty, then return true
        if (controlValue == null || controlValue.Trim().get_Length() == 0) {
            return true;
        }
        else {
            // Else try running the Regular Expression against the value 
            // and see if there is a match.
            try {
                System.Text.RegularExpressions.Match regExpMatch 
                    = System.Text.RegularExpressions.Regex.Match(controlValue,
                    this.get_ValidationExpression());
                return regExpMatch.get_Success() 
                    && regExpMatch.get_Index() == 0 
                    && regExpMatch.get_Length() == controlValue.get_Length();
            }
            catch (System.Exception exp) {
                return true;
            }
        }
    } //EvaluateIsValid
} //CustomRegularExpressionValidatorEvaluateIsValid

The following code example demonstrates how to use the CustomRegularExpressionValidatorEvaluateIsValid control, defined in the preceding example, on a Web Forms page.

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 RegularExpressionValidator - EvaluateIsValid - VJ# Example</title>
    <script runat="server">
        void Button1_Click(Object sender, EventArgs e) 
        {
            if (get_Page().get_IsValid()) {
                Label1.set_Text("Page is valid.");
            }
            else {
                Label1.set_Text("Page is invalid!");
            }
        } //Button1_Click
    </script>
    </head>
    <body>
        <form id="Form1" method="post" runat="server">
            <h3>Custom RegularExpressionValidator - EvaluateIsValid - VJ# Example</h3>
       <table style="background-color:#eeeeee; padding:10">
          <tr valign="top">
             <td colspan="3">
                <asp:Label ID="Label1" 
                  Text="Enter a 5 digit zip code" 
                  runat="server"/>
             </td>
          </tr>
 
          <tr>
             <td colspan="3">
                <b>Personal Information</b>
             </td>
          </tr>
          <tr>
             <td align="right">
                Zip Code:
             </td>
             <td>
                <asp:TextBox id="TextBox1" runat="server"/>
             </td>
             <td>
                <aspSample:CustomRegularExpressionValidatorEvaluateIsValid
                  id="Regularexpressionvalidator1" 
                  runat="server"
                  ControlToValidate="TextBox1"
                  ValidationExpression="\d{5}"
                  ErrorMessage="Zip code must be 5 numeric digits"
                  Display="Static"
                  EnableClientScript="False" />
             </td>
          </tr>
          <tr>
             <td></td>
             <td>
                <asp:Button text="Button1" 
                  OnClick="Button1_Click" 
                  runat="server" ID="Button1"/>
             </td>
             <td></td>
          </tr>
       </table>
        </form>
    </body>
</html>

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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