Q: Why don't nullable relational operators return “bool?” instead of “bool“?
Nullable types are a new feature of C# 2.0.
When dealing with nullable types, if you write the following:
int? i = 15;
int? j = 16;
the type of
i == j
is a normal bool, rather than a bool? (ie nullable bool). Why?
A: In our initial designs, we spent a fair amount of time discussing what the behavior should be here, and how we should cross over from the three-valued nullable world to the two-valued “normal C#“ world.
Consider the following method:
void Process(int? p)
{
if (p == null)
{
// do some processing...
}
}
This seems like a very natural thing for a C# user to want to write. But if equality is three-valued, comparing anything to null always returns a null value (ie null isn't equal to anything), and therefore such a comparison can never succeed. Instead, the user would have to write:
if (!p.HasValue)
or something similar. We decided that the value of having a model that was consistent with the way users were used to dealing with reference null was pretty high, and therefore decided to make the relational operators return bool.
