Question

Is it possible to have a type constraint that is an “or” of two types instead of an “and”. An “and” is accomplished by putting a comma between the two types. But what about an “or”?

class Type1<T, U>
{
    public static Type1<T, U> New<V>( V v )
        where V : T, U
    {
        return new Type1<T, U>();
    }
}

So in the above example, the argument passed into New() must be both a T and a U. But I want it to be either a T or a U.

Answer 1

There is no way to express the “or” constraint in the manner you described. However you can emulate this by having two overloads one which accepts U and the other T. These two can then feed into a common function which handles T or U

class Type1<T, U> {
  public static Type1<T, U> New(U p) {
    return NewCore(p);
  }

  public static Type1<T, U> New(T p) {
    return NewCore(p);
  }

  private static Type1<T, U> New(object o) {  
    ...
  }
}

Not quite sure what you’d want to do with the T or U parameter though. Perhaps you could elaborate a bit