Question

I have simple base class with single static field. I have numerous classes that derive from this base class. When I create a derived class, it causes invocation of the base classes static ctor which initializes the static field (Works as expected). The problem is that when I create another derived class, that inherits from same base, the static field in the base is still null, why???? It was initialized by the first class I instantiated.

Should not static fields in base classes have global allocation and be visible (ie. shared) to all derived classes?

My model:

class Base<T>
{

 protected static object s_field = null;

 static Base { s_field = new object(); }
}

class Derived1<T> : Base<T>
{

}

class Derived2<T> : Base<T>
{

}

// ... later in the program

Derived1<int> instance1 = new Derived1<int>(); // initializes static field (s_field in base class) for all derived types

Derived2<double> instance2 = new Derived2<double>(); // the static field is null

(I can see this through the debugger, but should it not already have been initialized by previous line??)

Answer 1

Since you have changed your code i believe you need to understand how generics works in .NET.

Static in generics behaves a bit different than in normal cases. For each unique open type T you provide, the base class maintains unique static member value.

You create another instance of open type double for the same base class via Derived < double > then youll see the concept what i am talking about.

Here a sample code to demonstrate more clearly :

public class Base<T>
    {
        public static string str = null;

        static Base()
        {
            str = "hello";

            Console.WriteLine("Ctor cald");
        }
    }

    public class Derived1<T> : Base<T>{}
    public class Derived2<T> : Base<T> { }

    public partial class Program
    {
         public static void Main()
        {
            Derived1<int> derv = new Derived1<int>();
            Derived2<double> derv2 = new Derived2<double>();
            Derived2<double> derv3 = new Derived2<double>();


            Console.ReadKey();
        }      
    }  

Here you shall see only 2 calls for the static Ctor.