c# - Unable to use instance variable in a static method

Question

Why we cannot use instance variable in a static method? I know that static methods are called without creating instance of classes but what restricts the non static variable to be used in static method?

class MyClass
{
    // non-static instance member variable
    private int a;
    //static member variable
    private static int b;

    //static method
    public static void DoSomething()
    {
        //this will result in compilation error as “a” has no memory
        a = a + 1;
        //this works fine since “b” is static
        b = b + 1;
    }
}

Answer 1

Trying to put a non-static variable inside a static method makes the compiler wonder which instance of this variable should I really be updating? The static methods are not related to a class instance, so it will be impossible to call an instance variable on an instance when no instance exists.