Why does null exist in .NET?

Question

Why can values be null in .NET? Is this superior to having a guarantee where everything would have a value and nothing call be null?

Anyone knows what each of these methodologies are called?

Either way, I am not very knowledgeable on this, but wouldn't having a value for everything makes things easier, in terms of simplicity, i.e. eliminating null checks, and being able to write more streamlined algorithms that doesn't have to branch out for checks.

What are the pros and cons of each style in terms of performance, simplicity, parallellism, future-proofing, etc.

Answer 1

As appealing as a world without null is, it does present a lot of difficulty for many existing patterns and constructs. For example consider the following constructs which would need major changes if null did not exist

1. Creating an array of reference types ala: new object[42]. In the existing CLR world the arrays would be filled with null which is illegal. Array semantics would need to change quite a bit here
2. It makes default(T) useful only when T is a value type. Using it on reference types or unconstrained generics wouldn't be allowed
3. Fields in a struct which are a reference type need to be disallowed. A value type can be 0-initialized today in the CLR which conveniently fills fields of reference types with null. That wouldn't be possible in a non-null world hence fields whos type are reference types in struct's would need to be disallowed

None of the above problems are unsolvable but they do result in changes that really challenge how developers tend to think about coding. Personally I wish C# and .Net was designed with the elimination of null but unfortunately it wasn't and I imagine problems like the above had a bit to do with it.