Why doesn't the C# compiler throw for logical comparisons of null?

Question

I was eating lunch with a friend yesterday and they were complaining about `null` in C#. He stated that `null` was illogical. I decided to test his claims, so I tested some simple logical propositions: Console.WriteLine(null == null); //True //Console.WriteLine(null == !!null); //BOOM Console.WriteLine(10 >= null); //False Console.WriteLine(10 <= null); //False Console.WriteLine(!(10 >= null)); //True Console.WriteLine(!(10 <= null)); //True Checking equality seems straightforward and this is what I would expect. The greater/less than statements however are logical contradictions which I find really confusing! Shouldn't these throw? The negation operation throws as you would expect. If I try to run comparisons (aside from equality) using `null` in Ruby or Python I get a type error along the lines of "cannot compare a number to nil". Why doesn't C# do this?

Answer 1

Hi,

It is up to the complier to determine the rules when handling nulls. In C# they have decided that the comparison operators to return false as the value. Result is just a design choice made by the developer at the time. Each language will have it own interpretation as you have noticed and some allow you to customize the default behavior, such as, SQL.

MSDN Doc:https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/nullable-value-types#lifted-operators