Question

In C# I have a generic class:

public class MyGeneric<ParameterClass> where ParameterClass: MyGenericParameterClass, new() {
    public static int Variable;
}

Now in C++ if I instantiated a templated class with different parameters each complete class would get it’s own Variable, so I just can’t say

MyGeneric.Variable = 1; // invalid in C++

in C++, but seems like I can do so in C#.

I’d like to clarify…

If I have a generic with a static member variable is that variable shared among all generic instantiations?

Answer 1

Section 25.1.4 of the ECMA C# Language specification

A static variable in a generic class declaration is shared amongst
all instances of the same closed constructed type (§26.5.2), but is
not shared amongst instances of different closed constructed types.
These rules apply regardless of whether the type of the static
variable involves any type parameters or not.

You may see this blog post: Static fields in generic classes by Gus Perez

You can’t do that in C# as well.

MyGeneric.Variable = 1;

Consider the following example from ECMA Language Specification.

class C<V>
{
    static int count = 0;
    public C()
    {
        count++;
    }
    public static int Count
    {
        get { return count; }
    }
}
class Application
{
    static void Main()
    {
        C<int> x1 = new C<int>();
        Console.WriteLine(C<int>.Count);  // Prints 1 
        C<double> x2 = new C<double>();
        Console.WriteLine(C<double>.Count); // Prints 1 
        Console.WriteLine(C<int>.Count);  // Prints 1 
        C<int> x3 = new C<int>();
        Console.WriteLine(C<int>.Count);  // Prints 2 
    }
}