Code Inspection: '??' condition is known to be always null or not null
If you want to assign a value, pass an argument, or return from a method based on the nullability of an identifier, the clearest syntax you can use in these cases is the ?? (null-coalescing) operator.
However, redundant null-coalescing expressions produce dead code and impede readability. The left-hand operand is evaluated first, and if it is null, the right-hand operand is evaluated and the result becomes the result of the whole expression. As it follows from the logic of the ??
operator, using null
as the right-hand operand does not make sense. In the example below, Rider suggests removing the right-hand operand null
together with the ??
operator, because if the newCategory
is null, then null will be assigned to the Category
anyway:
Another situation when the null-coalescing operator is redundant is when the left-hand operand can never be null. In this case, the right-hand operand never gets reached and Rider suggests removing the unreachable code:
Suboptimal code | After the quick-fix |
---|---|
string name = "John";
Console.WriteLine(name ?? "empty"); | string name = "John";
Console.WriteLine(name); |