Question

Func<T, TResult> delegate is for a delegate with a single param and return type of TResult.

Is this a special delegate or is it something we can code ourselves manually?

e.g. could I create a Func<T, TResult> but that accepts 2 input params?

Answer 1

"Func" is actually a family of classes in the System namespace, namely:

Func<TResult> (0 params), Func<T,TResult> (1 param), Func<T1,T2,TResult> (2 params) … Func(17) (16 params).

There are 17 different “Func” classes total, supporting from 0 to 16 parameters. It is allowable for them to share the name in code (“Func”) even though they are actually different types (Func, Func', Func'', etc) thanks to how Generics work in .NET — the number of generics determines/disambiguate which actual type is used.

Happy coding.

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As far as converting between delegates, this may be of use (runs in LINQPad, “C# Program”):

delegate int MyDelegate (int y);

void Main()
{
    Func<int,int> fun1 = (q) => q * q;
    MyDelegate del = new MyDelegate(fun1); // Convert the "Func" delegate to custom...
    Func<int,int> fun2 = new Func<int,int>(del); // ...and back
}