How can I rewrite the ErrorMessage for a CustomValidator control on the client?

Question

I have a CustomValidator that is validating a telephone number for several different telephone numbering schemes. The client-side javascript looks like this:

validatePhoneNumber(sender, args) {
    cleanNumber = args.Value.replace(/\D/, "");
    country = $("#" + CountryID).get(0).value;
    switch (country) {
        case "North America":
            args.IsValid = validateNAPhoneNumber(cleanNumber);
            if (!args.IsValid) sender.errormessage = "* Not a NA Phone #";
            break;
        case "UK":
            args.IsValid = validateUKPhoneNumber(cleanumber);
            if (!args.IsValid) sender.errormessage = "* Not a UK Phone #";
            break;
...
    }
}

The actual validation takes place properly, and the CustomValidator has the correct IsValid property at all times. The sender.errormessage, however, seems to be rewritten just after this function call to it's default value. How can I change the errormessage value, and make it "stick"?

Answer 1

function dateofbirth(sender, args) {

    var dtcDOB = document.getElementById('<%= dtcDOB.ClientID %>');

    var dob = new Date(dtcDOB.value);
    var currDate = new Date();

    if (dtcDOB.value == "") {
        args.IsValid = false;
        sender.textContent = "Provide DOB.";
        return;
    }

    args.IsValid = true;
}

Try sender.textContent = "your err msg". It worked for me.