Sometime you might want to use null as a parameter but you get the annoying CS0121.
The call is ambiguous between the following methods or properties…
One could just adjust constructor but that would be an easy way out.
Proper way would be to use default operator. For example, if you want to use null string, you can use something like
var dummy = new Dummy(default(string));
If we're using nullable reference types, just add question mark:
var dummy = new Dummy(default(string?));
And this simple trick selects the correct constructor every time.