The second + is converting the char to an int, and adding it into the string. The ASCII value for / is 47, which is then converted to a string by the other + operator.
The + operator before the slash implicitly casts it to an int. See + Operator on MSDN and look at the “unary plus”.
The result of a unary + operation on a numeric type is just the value of the operand.
I actually figured this out by looking at what the + operators were actually calling. (I think this is a ReSharper or VS 2015 feature)
