what is object keyword

I think this an interesting way to make vivid what object/Object in .NET is: in VisualStudio in .NET: put something like this in code somewhere, set a breakpoint, then compile and run, and examine the values:

bool intValue = 32 is object;
bool stringValue = "hello" is object;

And notice that Intellisense will give you a pre-compile message pop-up over the right side of the equal operator that this expression is always true.

Ask yourself: what must be true if every .NET Type is-a object ?

Whoops: did I say 'every:' then ask yourself what it means that

bool nullValue = null is object; // => false

So, 'null' is not an object !

You want to get fancy: what about nullable types ? What do you think happens:

int? myNullInt = null; // compare with setting myNullInt = 32;

bool nullableType = myNullInt is object;

If you wanted to get philosophical, perhaps you might paraphrase Pascal, and say: "object/Object in .NET is that Type whose center is everywhere, and whose circumference is nowhere." With "nowhere" equal to null :)