Question

I have the following code in C#:

Action a = new Action(() => Console.WriteLine());
dynamic d = a;
d += "???";
Console.WriteLine(d);

and the output is

System.Action???

while if you add an int instead of a string to d it would throw an exception.

Can you please explain why does this happen?

Answer 1

I think this happens because when you use d += "???"; d is converted to string (using default ToString() method which takes object name) and then “???” is appended and wrote to console.
If you try to use d += 2 this fails because there’s no default way to convert an Action to an integer. Same for other types…