Question

I’d like to write a generic method that creates a new instances of a specified Type. I tried

protected T CreateNew<T>()     where T : new() {     return new T(); } 

This works, but only if I specified the type at compile time, just like

var x = CreateNew<Point>(); 

The point is, that I need to do something like this

ISomeInterface inter; if (selection == 1)     inter = new SomeClass(); else     inter = new SomeClass2(); // ... ISomeInterface inter2 = CreateNew<typeof(inter)>(); 

where SomeClass implements ISomeInterface. But this fails to compile as CreateNew() needs an actual type specified. I don’t know if it’s possible to provide something like that at runtime, but the above code fails to compile.

So I have an instance of an unknown reference type and I need to create several instances of the same type.

Does anyone know a technique to achive this behaviour?

Answer 1

You can do it using a lambda:

Function<ISomeInterface> creationDelegate; if (selection == 1)     creationDelegate = () => CreateNew<SomeClass>; else     creationDelegate = () => CreateNew<SomeClass2>; ISomeInterface inter = creationDelegate();  // ... ISomeInterface inter2 = creationDelegate(); 

I can’t see the benefit of using the CreateNew method in this case based on your example code, but I’m assuming that your ‘real’ code is more sophisticated.