void in C# generics?

Question

I have a generic method that takes a request and provides a response.

public Tres DoSomething(Tres response, Treq request)
{/*stuff*/}


        

Answer 1

You could simply use Object as others have suggested. Or Int32 which I have seen some use. Using Int32 introduces a "dummy" number (use 0), but at least you can't put any big and exotic object into an Int32 reference (structs are sealed).

You could also write you own "void" type:

public sealed class MyVoid
{
  MyVoid()
  {
    throw new InvalidOperationException("Don't instantiate MyVoid.");
  }
}

MyVoid references are allowed (it's not a static class) but can only be null. The instance constructor is private (and if someone tries to call this private constructor through reflection, an exception will be thrown at them).

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Since value tuples were introduced (2017, .NET 4.7), it is maybe natural to use the struct ValueTuple (the 0-tuple, the non-generic variant) instead of such a MyVoid. Its instance has a ToString() that returns "()", so it looks like a zero-tuple. As of the current version of C#, you cannot use the tokens () in code to get an instance. You can use default(ValueTuple) or just default (when the type can be inferred from the context) instead.