Validation ASP.Net Tutorial

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  4. You can associate a custom validation function with the CustomValidator control
ControlToValidate:        The ID of the  form field being validated.
Text:                     The error message.
ClientValidationFunction: The name of a client-side function.
ServerValidate:           This event raised when the CustomValidator performs validation.
<%@ Page Language="C#" %>
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

    void valComments_ServerValidate(Object source, ServerValidateEventArgs args)
    {
        if (args.Value.Length > 10)
            args.IsValid = false;
        else
            args.IsValid = true;
    }



    Show CustomValidator


    
    

            id="lblComments"
        Text="Comments:"
        AssociatedControlID="txtComments"
        Runat="server" />
            id="txtComments"
        TextMode="MultiLine"
        Columns="30"
        Rows="5"
        Runat="server" />
            id="valComments"
        ControlToValidate="txtComments"
        Text="(Comments must be less than 10 characters)"
        OnServerValidate="valComments_ServerValidate"
        Runat="server" />
            id="btnSubmit"
        Text="Submit"
        Runat="server" />