Cannot implicitly convert type 'int' to 'short' [duplicate]

Answer 1

The problem is, that adding two Int16 results in an Int32 as others have already pointed out.
Your second question, why this problem doesn't already occur at the declaration of those two variables is explained here: http://msdn.microsoft.com/en-us/library/ybs77ex4%28v=VS.71%29.aspx:

short x = 32767;

In the preceding declaration, the integer literal 32767 is implicitly converted from int to short. If the integer literal does not fit into a short storage location, a compilation error will occur.

So, the reason why it works in your declaration is simply that the literals provided are known to fit into a short.

Answer 2

Adding two Int16 values result in an Int32 value. You will have to cast it to Int16:

Int16 answer = (Int16) (firstNo + secondNo);

You can avoid this problem by switching all your numbers to Int32.

Answer 3

For some strange reason, you can use the += operator to add shorts.

short answer = 0;
short firstNo = 1;
short secondNo = 2;

answer += firstNo;
answer += secondNo;