RegularExpressionValidator.EvaluateIsValid Method
Definition
Important
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Indicates whether the value in the input control is valid.
protected:
override bool EvaluateIsValid();protected override bool EvaluateIsValid ();override this.EvaluateIsValid : unit -> boolProtected Overrides Function EvaluateIsValid () As BooleanReturns
true if the value in the input control is valid; otherwise, false.
Examples
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.
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.
using System.Web;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
[AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
public sealed class CustomRegularExpressionValidatorEvaluateIsValid : System.Web.UI.WebControls.RegularExpressionValidator
{
protected override bool EvaluateIsValid()
{
// Get the control to validate's validation value
string controlValue = GetControlValidationValue(this.ControlToValidate);
// If the value is null or empty, then return true
if (controlValue == null || controlValue.Trim().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.ValidationExpression);
return(regExpMatch.Success && regExpMatch.Index == 0 && regExpMatch.Length == controlValue.Length);
}
catch
{
return true;
}
}
}
}
}
Imports System.Web
Imports System.Security.Permissions
Namespace Samples.AspNet.VB.Controls
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomRegularExpressionValidatorEvaluateIsValid
Inherits System.Web.UI.WebControls.RegularExpressionValidator
Protected Overrides Function EvaluateIsValid() As Boolean
' Get the control to validate's validation value
Dim controlValue As String = GetControlValidationValue(Me.ControlToValidate)
' If the value is null or empty, then return true
If controlValue Is Nothing OrElse controlValue.Trim().Length = 0 Then
Return True
Else
' Else try running the Regular Expression against the value
' and see if there is a match.
Try
Dim regExpMatch As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(controlValue, Me.ValidationExpression)
Return regExpMatch.Success AndAlso regExpMatch.Index = 0 AndAlso regExpMatch.Length = controlValue.Length
Catch
Return True
End Try
End If
End Function
End Class
End Namespace
The following code example demonstrates how to use the CustomRegularExpressionValidatorEvaluateIsValid control, defined in the preceding example, on a Web Forms page.
<%@ 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 RegularExpressionValidator - EvaluateIsValid - C# Example</title>
<script runat="server">
void Button1_Click(Object sender, EventArgs e)
{
if (Page.IsValid)
{
Label1.Text = "Page is valid.";
}
else
{
Label1.Text = "Page is invalid!";
}
}
</script>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom RegularExpressionValidator - EvaluateIsValid - C# 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>
<%@ 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 RegularExpressionValidator - EvaluateIsValid - VB.NET Example</title>
<script runat="server">
Sub Button1_Click(sender As Object, e As EventArgs)
If Page.IsValid Then
Label1.Text="Page is valid."
Else
Label1.Text="Page is not valid!"
End If
End Sub
</script>
</head>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom RegularExpressionValidator - EvaluateIsValid - VB.NET 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>
Applies to
See also
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