Question

I have some classes that all implement a certain interface. I want to store a unique string in each class that I can get without creating an object for that class. I searched through a lot of posts here already and couldn’t find an answer.

If I create an object for each class, then what I want is simply:

    class X:IBase{ string m = "x";}

    class Y:IBase{string m = "x";}

    class Z:IBase{string m = "x";}

    class interface IBase{ string m;}

    static int Main(){
      IBase[] arr = {new X(), new Y(), new Z()};
      foreach(IBase b in arr){
          Console.WriteLine(b.m);
      }
    }

But I want to do this without creating an object. So I want to do this:

    class X:IBase{ static string m = "x";}

    class Y:IBase{ static string m = "x";}

    class Z:IBase{ static string m = "x";}

    class interface IBase{ //no static fields allowed}

    static int Main(){
      Type[] arr = {X, Y, Z};
      foreach(Type t in arr){
          Console.WriteLine(t.m); //error, cannot resolve symbol m
      }
    }

Am I missing something obvious or is this just impossible?

The reason I don’t want to create an object is because I want to display this string at the start, when I don’t need any objects. I only create an object when I need to to save space.

Answer 1

Reflection is your friend:

interface IBase { }
class X : IBase { static string m = "x";}    
class Y : IBase { static string m = "y";}    
class Z : IBase { static string m = "z";}

static void Main()
{
    Type[] arr = { typeof(X), typeof(Y), typeof(Z) };
    foreach (Type t in arr)
    {
        FieldInfo fieldInfo = t.GetField("m", 
                BindingFlags.Static | BindingFlags.NonPublic);
        Console.WriteLine(fieldInfo.GetValue(null));
    }
}

Note how Type[] arr = {X, Y, Z}; has been changed into Type[] arr = { typeof(X), typeof(Y), typeof(Z) }; in order to get the Type object for each of the types.