Nullable reference types with generic return type

Question

I\'m playing around a bit with the new C# 8 nullable reference types feature, and while refactoring my code I came upon this (simplified) method:

public T Get         


        

Answer 1

You were very close. Just write your method like this:

[return: MaybeNull]
public T Get(string key)
{
    var wrapper = cacheService.Get(key);
    return wrapper.HasValue ? Deserialize(wrapper) : default!;
}

You have to use the default! to get rid of the warning. But you can tell the compiler with [return: MaybeNull] that it should check for null even if it's a non-nullable type.

In that case, the dev may get a warning (depends on flow analytics) if he uses your method and does not check for null.

For further info, see Microsoft documentation: Specify post-conditions: MaybeNull and NotNull