Why can't I call a public method in another class?

Question

I have got these two classes interacting and I am trying to call four different classes from class one for use in class two.

The methods are public and they do return va

Answer 1

For example 1 and 2 you need to create static methods:

public static string InstanceMethod() {return "Hello World";}

Then for example 3 you need an instance of your object to invoke the method:

object o = new object();
string s = o.InstanceMethod();