Question

I’m using MiscUtil Operators for a while without any big problems. But now i found something that really bothers me:

byte first = 13;
byte second = 29;

byte result = MiscUtil.Operator.Add(first, second);

The simple expected result of this equation should be result == 42 but unfortunately this throws an InvalidOperationException:

The binary operator Add is not defined for the types 'System.Byte' and 'System.Byte'.

By taking a closer look at this odd behavior you’ll find out that System.Byte really doesn’t implement these operators. Within C# these types will be implicitly converted to an Int32 and that does implement these operators.

So the question is now: Is there any chance to get MiscUtil to work with byte and sbyte?

Answer 1

Technically, int etc also don’t implement these operators. They are not provided by “operators” in the normal sense (which would involve a static-call), but represented directly by the add op-code. Ultimately, the failure in this case is actually coming from the Expression API:

var x = Expression.Parameter(typeof(byte));
var y = Expression.Parameter(typeof(byte));
var func = Expression.Lambda<Func<byte,byte,byte>>(
    Expression.Add(x,y), x, y).Compile(); // explodes here

To fix it, MiscUtil would have to special-case the byte/sbyte versions; something like:

var x = Expression.Parameter(typeof(byte));
var y = Expression.Parameter(typeof(byte));
var func = Expression.Lambda<Func<byte,byte,byte>>(
    Expression.Convert(
        Expression.Add(
            Expression.Convert(x, typeof(int)),
            Expression.Convert(y, typeof(int))
         ),typeof(byte)), x, y).Compile();

However! It has been a long time since I knew my keys for Jon’s repo ;p

Oddly enough, though, it isn’t all that hard to implement the entire thing in raw IL… I actually stumbled into (on a USB-drive) a very old .NET 2.0 (i.e. before Expression) version of “generic operators” that I wrote many many years ago, which might do the job. Or easier: just patch MiscUtil locally to handle byte/sbyte.