Question

Isn’t var a keyword in C#? But why can I do this:

public class var { }

public class main
{
    public static void main(string[] args)
    {
        var testVar = new var();
    }
}

The var that is used in the code is the var class that is declared before the main class. And the compiler doesn’t even complain.

While when I do this:

public class int { }

or this:

public class true { }

The compiler said that int or true is a keyword and cannot be used like that. Why is it not the same with var?

Answer 1

var is not a keyword according to this list.

it is a contextual keyword, so from the context, the compiler is able to decide which is your class and which is the contextual keyword, and no confusion arises.

a contextual keyword is:

used to provide a specific meaning in the code, but it is not a
reserved word in C#.

so as it’s not reserved you can use it.

As pointed out in the comments above there is a discussion of the differences as well as a list of the various keywords and contextual keywords added at each version of c# on Eric Lippert’s blog

It is interesting to note that since the set of keywords was decided upon in C#1.0 there have been no additions, so as to preserve backward compatibility.