Question

I have a class with several constructors and I want to call the “main” one from another – but using null.

Using just this(null) results in a compile time error, so I cast null to the type of the other constructor. Compiles fine.

MyClass
{
  public MyClass(SomeType t)
  { }

  public MyClass(IList<FooType> l)
    : this((SomeType)null)
  { }
}

This feels, lets just say icky. Is this okay and common or insane and shows a flaw in the class – in that it should have an empty constructor?

The class “mostly” requires a SomeType, but there are rare times when it is okay to not have one. I want the rare times to “stick out” and be obvious that something “is not a-typical” with the code.

Answer 1

You need the cast because null by itself is ambiguous. A null by itself has no inherent type, so the cast tells the compiler which constructor you want to pass null to.

That being said, it is probably more meaningful for your class to use a default (no-arg) constructor, like you said. Having all three constructors is probably okay, too.