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Asked: 2026-05-16T23:41:05+00:00

I am adding a custom validator to the page programmatically on click of a

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I am adding a custom validator to the page programmatically on click of a button, then validating the page and checking the IsValid property of the page. but the IsValid property is always returning true. Please help. here is the code. I need to add custom validator dynamically to show validation messages from business object. I am setting the IsValid property of the custom validator to false, so I expect the IsValid property of the Page to return false as well after validation. can’t understand what I am doing wrong here.

    protected void Button1_Click(object sender, EventArgs e)
{
    var validator = new CustomValidator();
    validator.IsValid = false;
    validator.ErrorMessage = "The input is invalid";
    validator.ValidationGroup = "vgCustom";
    Page.Validators.Add(validator);
    ValidationSummary1.ValidationGroup = "vgCustom";
    Page.Validate("vgCustom");
    Label1.Text = Page.IsValid ? "The Page is valid" : "The Page is Invalid";
}

and here is the HTML mark-up

<html xmlns="http://www.w3.org/1999/xhtml" >
 <head runat="server">
    <title></title>
 </head>
 <body>
    <form id="form1" runat="server">
    <div>
        <asp:ValidationSummary ID="ValidationSummary1" runat="server"/>
        <asp:Button ID="Button1" runat="server" Text="Validate" OnClick="Button1_Click" />
        <asp:Label ID="Label1" runat="server"></asp:Label>
    </div>
    </form>
 </body>
</html>
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1 Answer

  1. Editorial Team

    BaseValidator.Validate Method:

    Use the Validate method to perform
    validation on the associated input
    control. This method allows you to
    programmatically perform validation on
    the input control. The IsValid
    property is automatically updated with
    the validation results.

    So validator.IsValid is being reset to its default value (True) when you call Page.Validate("vgCustom"). Whereas with the ServerValidateEventHandler, your code is setting IsValid on Page.Validate("vgCustom") instead of letting it be reset to the default. If you move validator.IsValid = false to after the call to Page.Validate("vgCustom"), the page should fail to validate as expected.

    I prefer to use the following pattern though:

    /// <summary>
/// A validator that fails unconditionally. Useful if you need to do
/// validation entirely in the code-behind, yet still integrate with
/// the standard ASP.NET validation framework.
/// </summary>
public class FailValidator : BaseValidator {
    protected override bool ControlPropertiesValid() {
        // make setting ControlToValidate optional
        return true;
    }

    protected override bool EvaluateIsValid() {
        return false;
    }
}
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