Why does C# issue the error “cannot implicitly convert int to ushort” against modulo arithmetic on ushorts?

Question

In another thread, someone asked about why adding two ushort values raised errors in C#. e.g.

ushort x = 4;
ushort y = 23;
ushort z = x+y;  // E         


        

Answer 1

The % operator that's being used, even with shorts or ushorts, has a signature of int %(int a, int b). So your shorts are being lifted up into integers, and your result is an integer you are attempting to assign to a ushort, which is a lossy cast so you are required to be explicit.

Consider this:

ushort x = 5;
ushort y = 6;
var res = x % y;
Console.WriteLine(res.GetType()); // System.Int32
ushort z = res; // cast error, explicit conversion exists
ushort zz = (ushort)res; // Fine, we cast down.