Can I initialize var with null or some empty value?
A var cannot be set to null since it needs to be statically typed.
var foo = null;
// compiler goes: "Huh, what's that type of foo?"
However, you can use this construct to work around the issue:
var foo = (string)null;
// compiler goes: "Ah, it's a string. Nice."
I don't know for sure, but from what I heard you can also use dynamic instead of var. This does not require static typing.
dynamic foo = null;
foo = "hi";
Also, since it was not clear to me from the question if you meant the varkeyword or variables in general: Only references (to classes) and nullable types can be set to null. For instance, you can do this:
string s = null; // reference
SomeClass c = null; // reference
int? i = null; // nullable
But you cannot do this:
int i = null; // integers cannot contain null