MVC2 Ajax not working in Firefox – Error “a is undefined”

I was using MVC2 Ajax function with “this.form.onsubmit()”, it works on IE but not firefox, it causes an error “a is undefined” in /scripts/MicrosoftAjax.js    Line 6

if I use /scripts/MicrosoftAjax.debug.js , it says “Sys.ArgumentUndefinedException: Value cannot be undefined. Parameter name: eventObject”

The solution is here  solved by tpeczek.

1. add a hidden submit button in the form, for example:

<inputtype=submit id=”AJAXSubmitButton”name=”AJAXSubmitButton”value=”Update”style=”display:none;/>

2. change ajax call function to


so you are forcing the submit button to be clicked, to submit the ajax form.