How to use typeof or GetType() as Generic's Template?

Question

If it harder to explain using words, let's look at an example I have a generic function like this

void FunctionA<T>() where T : Form, new()
{
}

If I have a reflected type, how do I use it with the above function? I'm looking forward to do this

Type a = Type.GetType("System.Windows.Forms.Form");
FunctionA<a>();

Of cause the above method doesn't working.

Answer 1

You can't. Generics in .NET must be resolved at compile time. You're trying to do something that would resolve them at runtime.

The only thing you can do is to provide an overload for FunctionA that takes a type object.

---

Hmmm... he's a dick, but he's right.

class Program
{
    static void Main(string[] args)
    {
        var t = typeof(Foo);
        var m = t.GetMethod("Bar");
        var hurr = m.MakeGenericMethod(typeof(string));
        var foo = new Foo();
        hurr.Invoke(foo, new string[]{"lol"});
        Console.ReadLine();
    }
}

public class Foo
{
    public void Bar<T>(T instance)
    {
        Console.WriteLine("called " + instance);
    }
}

MakeGenericMethod.

Answer 2

Actually, this is not correct. Generic types can be instantiated at run-time in .NET.

Use MethodInfo.MakeGenericMethod

Answer 3

class Program { static void Main(string[] args) { int s = 38;

        var t = typeof(Foo);
        var m = t.GetMethod("Bar");
        var g = m.MakeGenericMethod(s.GetType());
        var foo = new Foo();
        g.Invoke(foo, null);
        Console.ReadLine();
    }
}

public class Foo
{
    public void Bar<T>()
    {
        Console.WriteLine(typeof(T).ToString());
    }
}

it works dynamicaly and s can be of any type