[jQuery] (Validation) how to add validation on a select box with auto post

[jQuery] (Validation) how to add validation on a select box with auto post


Hi,
I have a select box with and onchange event to get the data from
serever,
<SELECT name="States" id="State"     onchange="getData(this.value)" >
Now i want to validate that if no value is selected from the above
list, then it should not send the ajax request. How can i apply the
Jquery validation plugin here?
Thanks.