We recently overhauled InMemory.Net to add improved support for NULL operations.
In general now we have added null support for most expressions. All functions should also accept null parameters, and return null if their parameters are null. You can also use cast with null, e.g. cast ( null as bigint ) to force a null of a specific type.
MIN and MAX aggregate functions should also handle nulls correctly. Basic arithmetic should also propagate nulls. E.g. 2+ NULL should return NULL now.
Conditions also should now only evaluate true if both parameters are not null.