Question

In C# can I pass a delegate an argument list for a class constructor in a fairly concise way?

I know this is extremely situational and may seem a bit of an odd request, also it’s not for the factory pattern. If it helps think of it as a challenge. The correct answer to this question may be that it is not possible.

Func<MyClassConstructionArgsType, MyClass> make_MyClass =
    args => {return new MyClass(args);};

var n = make_MyClass(comma separated arguments);

I also need there to not be a copy of the description of what the arguments are, the below for example is not a solution:

Func<int, string, MyClass> make_MyClass =
    (a, b) => {return new MyClass(a, b);};

Or, for the same reasons this:

Class Args
{
    ...
}

Func<Args, MyClass> make_MyClass =
    a => {return new MyClass(a);};

var n = make_MyClass(Args(args));

Dito where this is the case:

var n = make_MyClass<MyClass>(comma separated arguments);

The Object[]{comma separated arguments} approach is good except that optional parameters also need to be supported.

This question was created as a result of Anastasiosyal’s answer from the following question: c# class reference as opposed to instance reference

Josh first answer seems as close as is possible in C#.

Answer 1

Not without some form of reflection.

You could create a delegate that uses Activator:

Func<Object[], MyClass> makeClass =
   args => (MyClass) Activator.CreateInstance(typeof (MyClass), args);

makeClass(new object[] {"String", 32});

But this is as close as you can get using a delegate. However, if you create a static helper you can make this much nicer to look at:

public static T BuildType<T>(params Object[] args) {
   return (T) Activator.CreateInstance(typeof (T), args);
}

BuildType<MyClass>("String", 32);

Again, without reflection I’m not sure you can really achieve what you want.