What's wrong with this expression? Cannot implicitly convert type 'int' to 'byte'

Question

I am getting the error "Cannot implicitly convert type 'int' to 'byte'. An explicit conversion exists (are you missing a cast?)". Doesn't byte + byte = byte? Also I notice when I remove the +rgb.Green it works

// rgb.Red, rgb.Green, rgb.Blue are byte types
// h, delta are double
rgb.Red = Convert.ToByte(Math.Round((h - 4) * delta)) + rgb.Green;

public struct RGBColor
{
    public byte Red { get; set; }
    public byte Green { get; set; }
    public byte Blue { get; set; }
}

Answer 1

Adding two bytes produces an integer in C#. Convert the entire thing back to a byte.

rgb.Red = (byte)(Convert.ToByte(Math.Round((h - 4) * delta)) + rgb.Green);

See byte + byte = int... why? for more information.

Answer 2

Doesn't byte + byte = byte?

Nope, because it may overflow (> 255), that's why this operation returns an Int32. You could cast the result back to byte at your own risk.