I have an application android application it is using API deployed on IIS using .NET , is there any tool which I can use to check which function is called by android button click with what parameters ? basically I want to test the application right now My API is having try catch block but in catch I am having exception ex (ex.Message) which gives error object reference is not set to an instance of object but it is not showing for which column it is not able to get the value this error is normally due to null values .