Add conditional to a null coalescing operation

October 25, 2023

I have an existing method return using a null-coalescing operation:

return GetOverrideColor(overrideFlags, colorUsage) ??
       GetColor(colorExpression, field, purpose, defaultColor);

Is there a way to add an additional condition to this shorthand that would only run the GetOverrideColor method if x = true?

This is what I have in longhand:

CustomColor color = null;

if (overrideRequired)
    color = GetOverrideColor(overrideFlags, colorUsage);

if (color == null)
    color = GetColor(colorExpression, field, purpose, defaultColor);

return color;

>Solution :

I think you’re looking for this:

return (overrideRequired ? GetOverrideColor(overrideFlags, colorUsage) : null) ??
       GetColor(colorExpression, field, purpose, defaultColor);

If overrideRequired is false, null is used for the left-hand operand to ??. If it’s true, GetOverrideColor(overrideFlags, colorUsage) is called and used as the left-hand operand to ??.

Alternatively, you might update GetOverrideColor to accept a flag for this (perhaps one of overrideFlags?), though calling a function passing in a value that tells it to just immediately return null may be a bit off…