How to access all specific versions of a generic static class in C#?

Question

Let's say I have the following static class:

public static class Foo<T>
{
    private static T Baz;

    /* other members */

    public static void Bar()
    {
        //do something with Baz
    }
}

Is there a built-in way to call Bar() for all specific versions of the generic class without knowing the type parameters that were used? That is, if the consumer of Foo<T> has used it as Foo<Larry>, Foo<Curly> and Foo<Moe>, how can I call all the Foo<Larry>.Bar(), Foo<Curly>.Bar() etc. methods automatically without explicitly specifying the generic types?

This isn't possible. What actual problem are you trying to solve? Perhaps there's a better way. — Charles Mager, May 10 '15 at 20:43

score 1 · Accepted Answer · answered May 10 '15 at 20:42

1

That is not possible. Use the static constructor of Foo<T> to maintain a global list of Baz values. That global list must be rooted in a static variable that lives outside of Foo<T>.

answered May 10 '15 at 20:42

usr

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Thanks, I've used the same approach, but wanted to learn if there was a better way. – Alexey May 10 '15 at 21:15
Sure, I find your question to be valid. – usr May 10 '15 at 21:21
@Alexey You could have a `public static readonly List BarActions` in another (non-generic) class, and just use `static Foo() { OtherClass.BarActions.Add(Bar); }`. – Jeppe Stig Nielsen May 10 '15 at 21:30
False. Is possible (and not very difficult). See my answer – MatteoSp May 10 '15 at 21:50

score 0 · Answer 2 · answered May 11 '15 at 16:24

The number of possibilities for T is infinite. There is no way to know what might be used for T. You can, using the static constructor, track the types that have already been used for T and perform an operation against all of those types.

Here I created a class with a static variable containing a list of Actions. Action matches the signature of void Bar(), so to call a different signature, use a different type i.e. Action<string> to call void Bar(string x) or Func<int,string> to call string Bar(int val).

public static class FooTracker
{
    public static List<Action> AllBars = new List<Action>();
    public static void CallAllBars()
    {
        AllBars.ForEach(v => v());
    }
}

public static class Foo<T>
{
    static Foo()
    {
        FooTracker.AllBars.Add(() => Bar());
    }

    public static void InitFoo() 
    { 
        // do nothing other than cause static constructor to run
    }


    private static T Baz;

    /* other members */

    public static void Bar()
    {
        //do something with Baz
        Debug.Print(typeof(T).Name);
    }
}

If you use the code below to call this, you will observe that Foo<Curly>.Bar() isn't called because the static constructor isn't run until after the CallAllBars() call.

Foo<Larry>.InitFoo();
Foo<Moe>.InitFoo();

FooTracker.CallAllBars();

Foo<Curly>.InitFoo();

Why did you write `FooTracker.AllBars.Add(() => Bar());` instead of `FooTracker.AllBars.Add(Bar);`? — Alexey, May 13 '15 at 08:01
No reason, just some bad habits of mine. Functionally it works the same but I think your version compile to better code, although I find my version easier to read. — Grax32, May 13 '15 at 10:42

How to access all specific versions of a generic static class in C#?

2 Answers2

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