Programming Forums > Application Development > C#

Robocop · Apr 13th, 2008, 1:17 PM

Can somebody tell me what's the difference between the 'var' and 'object' keywords in c#?

Jimbo · Apr 13th, 2008, 1:36 PM

'object' is a keyword because someone thought it would be cool to have a keyword for the System.Object type. It's the same with 'string' (not to be confused with Object and String respectively, since those are the class names, not keywords).

var is a keyword to denote that the type is whatever the assignment expression returns. It can be re-typed through various assignments too. Take the following:

 c# Syntax (Toggle Plain Text) 
var foo;
foo = new String();
foo = new List<int>();
var foo;
foo = new String();
foo = new List<int>();

The compiler will determine the type of foo each time it is assigned to. Works pretty handy for anonymous types too

xavier · Apr 13th, 2008, 11:42 PM

really ?
From what I've read ,once you go
var foo = "";
... you can never go back

.

In other words foo = new List<int>() - won't work because the language is still strongly typed, and will say can't assign List<> to string .. or something like that.

So the var keyword is a simpler way to declare stuff . so you don't have to go:
List<Dictionnary<int,List<string>>> myWeirdList = new List<Dictionnary<int,List<string>>>();

And useful for anonymous types.

Jimbo · Apr 14th, 2008, 12:55 AM

Ah, you're right. I take that back, it's typed only on the first assignment.

Ooble · Apr 14th, 2008, 1:01 AM

Phew. I got confused there. I remembered reading about var when they first introduced it to the language, and it looked interesting. Then you told me that C# was actually dynamically typed and it blew my mind. :p

Apr 13th, 2008, 1:17 PM	#1
Robocop Programmer Join Date: Sep 2004 Posts: 42 Rep Power: 0	var vs object Can somebody tell me what's the difference between the 'var' and 'object' keywords in c#?

Apr 13th, 2008, 1:36 PM	#2
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 748 Rep Power: 3	Re: var vs object 'object' is a keyword because someone thought it would be cool to have a keyword for the System.Object type. It's the same with 'string' (not to be confused with Object and String respectively, since those are the class names, not keywords). var is a keyword to denote that the type is whatever the assignment expression returns. It can be re-typed through various assignments too. Take the following: c# Syntax (Toggle Plain Text) var foo; foo = new String(); foo = new List<int>(); var foo; foo = new String(); foo = new List<int>(); The compiler will determine the type of foo each time it is assigned to. Works pretty handy for anonymous types too __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

Apr 13th, 2008, 11:42 PM	#3
xavier Professional Programmer Join Date: Oct 2004 Location: .ro Posts: 373 Rep Power: 4	Re: var vs object really ? From what I've read ,once you go var foo = ""; ... you can never go back . In other words foo = new List<int>() - won't work because the language is still strongly typed, and will say can't assign List<> to string .. or something like that. So the var keyword is a simpler way to declare stuff . so you don't have to go: List<Dictionnary<int,List<string>>> myWeirdList = new List<Dictionnary<int,List<string>>>(); And useful for anonymous types. __________________ Don't take life too seriously, it's not permanent !

Apr 14th, 2008, 12:55 AM	#4
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 748 Rep Power: 3	Re: var vs object Ah, you're right. I take that back, it's typed only on the first assignment. __________________ <insert disclaimer here> <insert shameless plug for Visual Studio here>

Apr 14th, 2008, 1:01 AM	#5
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Re: var vs object Phew. I got confused there. I remembered reading about var when they first introduced it to the language, and it looked interesting. Then you told me that C# was actually dynamically typed and it blew my mind. :p __________________ Me :: You :: Them

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Programming Forums > Application Development > C#

var vs object