[jQuery] Validate

I am using jquery ajax to call asp.net page method. How can I use
jquery validation for such case when there is no form submission.
Here's the code portion used to call page method.
$.ajax({
type: "POST",
url: pagePath + "/" + fn,
contentType: "application/json; charset=utf-8",
data: paramList,
dataType: "json",
success: successFn,
error: errorFn
})