#1,199 – Equality and Inequality with Nullable Types

The equality and inequality operators work with nullable types as follows:

• If both operands are non-null, the operators are applied to the values
• If one operand is null and the other has a value, == returns false, != returns true
• If both operands are null, == returns true and != returns false

            int? val1 = 5;
            int? val2 = 10;
            int? val3 = null;
            int? val4 = null;
            int? val5 = 10;

            bool b1 = val1 == val2;   // False
            b1 = val2 == val5;        // True
            b1 = val1 == val3;        // False
            b1 = val1 != val3;        // True
            b1 = val3 == val4;        // True
            b1 = val3 != val4;        // False