Question

I’m looking at some code golf in LINQPad and wondering why:

int c;
string o;

o+=c;//this works

o+=P==2?"."+c:c;//this doesn't

o+=P==2?"."+c:""+c;//this does

mostly why the first one works and the second one throws a “no implicit conversion between ‘string’ and ‘int'” error.

Answer 1

Your second, non-working example has inconsistent types in the ?: operator. What you have is:

o += (P == 2 ? (string) "." + c : (int) c);

(The types in parentheses above are there to clarify what the existing types are, not to cast them to a different type.)

Both sides of the : in the ternary operator must be of the same type. For this reason, your second example is a syntax error. The third example works, because concatenating with an empty string coerces c into a string.