how to call method from cs page using ajax?

Question

I want to call the method which is in cs page using ajax.

Answer 1

What is 'cs page' ?
Did you refer to C sharp script? (so you better have to tag also C# or at least CS)
Or an accronym web site brand as Counter Strike? (so your request will rather be "how to use xxx API")
Or even about Adobe CS flavour apps?