How do I hook up javascript to my CustomValidator control in .Net

Question

I have created a CustomValidator control

public class MyValidator :CustomValidator, IScriptControl {}

and also created the equivalent client script. The server validation works fine, however how do I hook up my client script?

The rendered javascript looks like

var MyValidator1 = document.all ? document.all["MyValidator1"] : document.getElementById("MyValidator1");
MyValidator1.controltovalidate = "MyField";
MyValidator1.errormessage = "error";
MyValidator1.evaluationfunction = "MyValidatorEvaluateIsValid";

How do I override the generated javascript to set the value of evaluationfunction? E.g.

MyValidator1.evaluationfunction = "MyCustomJavascriptFunction";

Answer 1

I've answered this myself as the other answer didn't quite achieve exactly what I wanted. I ended up using.

public class MyValidator : BaseValidator, IScriptControl  {

  protected override void AddAttributesToRender(HtmlTextWriter writer) {
    base.AddAttributesToRender(writer);
    Page.ClientScript.RegisterExpandoAttribute(this.ClientID, "evaluationfunction", "MyJavascriptFunction");
  }

}

Which will cause the control to generate:

MyValidator1.evaluationfunction = "MyJavascriptFunction";

Answer 2

You can set the ClientValidationFunction property of the base class like this -

base.ClientValidationFunction = "MyCustomJavascriptFunction";

So, it will render it like this -

MyValidator1.evaluationfunction = "MyCustomJavascriptFunction";

You can do it from the control also by setting the same property.

EDIT: You can do

document.getElementById("<%= ValidatorId %>").evaluationfunction = "MyCustomJavascriptFunction";

Answer 3

Actually much easier is to use the ClientValidationFunction property of the asp:CustomValidator like below. Be sure NOT to specify a ControlToValidate property.

<asp:CustomValidator ClientValidationFunction="MyCustomJSFunction" Text="Required" ForeColor="Red"></asp:CustomValidator>

function MyCustomJSFunction(validator, args) {
    args.IsValid = my condition;
}