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

Answer 1

We've got Tony Hoare, an early pioneer that worked on Algol to thank for that. He rather regrets it:

I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.

A billion is a low-ball number, I think.

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UPDATE: C# version 8 and .NETCore have a decent solution for this problem, check out non-nullable reference types.