How to keep AjaxPro working after a postback?

[peruukki]

Hi guys,
thanks to this forum I solved the problem of calling a postback in javascript. Now I'm facing a new problem. After the page let's say MyForm.aspx where code is in the cs separate file, I got some AjaxPro code associated to a dropdownlist. To call it, I try to execute the instruction

MyForm.functionName(args, functionName_CallBack);

but debugger complaints as follows

Microsoft JScript runtime error: 'MyForm' is undefined.

What happens here, what should I do?

 

[peruukki]

Any idea? Thanks