Nullable reference types with generic return type

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

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

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