Why does C# allow you to 'throw null'?

Question

While writing some particularly complex exception handling code, someone asked, don\'t you need to make sure that your exception object isn\'t null? And I said, of course n

Answer 1

In older c#:

Consider this syntax:

public void Add ( T item ) => throw (hashSet.Add ( item ) ? null : new Exception ( "The item already exists" ));

I think it's way shorter than this:

public void Add ( T item )
{
    if (!hashSet.Add ( item ))
        throw new Exception ( "The item already exists" );
}