Why can I only access static members from a static function?

Question

I have a static function in a class.

whenever I try to use non static data member, I get following compile error.

An object reference is required for the non

Answer 1

Static functions can only use static members, and call static functions.

As mentioned, a static function can operate on a class instance, but not from within a class instance (for lack of a more descriptive word). For example:

class MyClass
{
    public int x;
    public static int y;

    public static void TestFunc()
    {
        x = 5; // Invalid, because there is no 'this' context here
        y = 5; // Valid, because y is not associated with an object instance
    }

    public static void TestFunc2(MyClass instance)
    {
        instance.x = 5; // Valid
        instance.y = 5; // Invalid in C# (valid w/ a warning in VB.NET)
    }
}