c# - Does casting null to string cause boxing? -

imagine code this:

var str = (string)null;

does differs from:

string str;

or:

string str = null;

does first code cause boxing of null value, or rather resolved @ compiler time string?

let's take question , pick apart.

will code in question cause boxing?

no, not.

this not because of 3 statements operate differently (there differences though, more below), boxing not concept occurs when using strings.

boxing occurs when take value type , wrap object. string reference type, , there never boxing involved it.

so boxing out, rest, 3 statements equal?

these 2 same:

var str = (string)null; string str = null;

the third 1 (second 1 in order of question though) different in sense declares str identifier of type string, not initialize null.

however, if field declaration of class, same since fields initialized defaults / zeroes when object constructed, , initialized null anyway.

if, on other hand, local variable, have uninitialized variable. judging fact write var ..., illegal in terms of fields, more correct question.

GCM