Create anonymous function using generic type parameters?

Question

Let's say I have this method:

int MyMethod(int arg)
{
    return arg;
}

I can create an anonymous equivalent of that like this:

Func<int, int> MyAnonMethod = (arg) =>
{
    return arg;
};

But let's say I have a method that uses generic type parameters like this:

T MyMethod<T>(T arg)
{
    return arg;
}

How can I create that as an anonymous method?

Answer 1

You have two choices:

1. You create a concrete delegate object, one that specifies the type of T
2. You declare the delegate in a generic context, using an existing T.

Example of the first

var f = new Func<int, int>(MyMethod<int>);
var result = f(10);

Example of the second

T Test<T>()
{
    T arg = default(T);
    Func<T, T> func = MyMethod; // Generic delegate
    return func(arg);
}

// Define other methods and classes here
T MyMethod<T>(T arg)
{
    return arg;
}

You will not be able to persuade the compiler or intellisense to carry the generic T with the delegate in a non-generic context and then work out the actual T when calling it.

So this is not legal:

void Test()
{
    var fn = new Func<T, T>(MyMethod<T>);
    fn(10); // returns 10
    fn("Test"); // returns "Test"
}