Why null-coalescing operator (??) in a mathematical function works different without parenthesis?

Question

Hello i have a doubt about this mathematical function in C# and i want to know why this happens. This two lines give different results, why?

container.price * (1 + (container.tax_rate / 100m)) * (1 - (container.promotion_rate ?? 0 / 100m))

Returns -> -839.9944

container.price * (1 + (container.tax_rate / 100m)) * (1 - ((container.promotion_rate ?? 0) / 100m))

Returns -> 50.99966

And the only difference in the function is the parenthesis on the second function: (container.promotion_rate ?? 0)

Answer 1

The null-coalescing operator has a lower precedence than the divide operator. Therefore, your code is interpreted as

 container.promotion_rate ?? (0 / 100m)

which gives you a different result.

MSDN Reference

Answer 2

/ has a higher precedence than ??.

Your first expression is parsed as container.promotion_rate ?? (0 / 100m)