Difference between Object, Var and Dynamic Keywords
| Object |
Var
|
Dynamic
|
Introduction:
Object
keyword is introduced in C# 1.0
|
Introduction:
Var
keyword is introduced in C# 3.0
|
Introduction:
Dynamic
keyword is introduced in C# 4.0
|
| Data
Storage:
Can
able to store any kind of value, because object is the base class
of all type in .net framework.
|
Data
Storage:
Can
able to store any type of value but it require to initialize at
the time of declaration.
|
Data
Storage:
Can
able to store any type of the variable, similar to old VB language
variable.
|
| Type
Safety:
Compiler
has little information about the type .
|
Type
Safety:
It's
compiler safe i.e compiler has all information about the stored
value, so that it doesn't cause any issue at run-time.
|
Type
Safety:
Compiler
doesn't have any information about the this type of variable.
|
| Supports
as method argument type :
Object
type can be passed as function argument and function also can
return object type
|
Supports
as method argument type :
Var
type can not be passed as function argument and function can not
return object type. This type of variable can work in the scope
where it defined.
|
Supports
as method argument type :
Dynamic
type can be passed as function argument and function also can
return object type
|
Need
type casting on assignment :
Require
to cast object variable to original type before using it. So this
assigning to object type and converting to original type called as
Boxing and Un-Boxing for value type and for the reference type its
casting of types. It's actually increasing the overhead when we do
this both operation.Allows to perform operation of given type once it get cast any user defined or primitive data type. |
Need
type casting on assignment :
No
need to cast because compiler has all information to perform
operation.
|
Need
type casting on assignment :
Casting
is not require but you need to know the property and methods
related to stored type
|
Stored
Value:
Cause
the problem at run time if the stored value is not get converted
to underlying data type.
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcycTv6ALhVrR_OunsRHEKvCYiTMKshkVU8wu-94nTU6nHaGXSGUJMek4phS92h9epYbo9_s4cTBL_HiPNX0Xrh8FbOtSuHBur98TlhBqEkWDX43EQDA6hBY6PlRmmNPywGUhmUDBDnzVS/s1600/Object+error.JPG
|
Stored
Value:
Doesn't
cause problem because compiler has all info about stored value.
|
Stored
Value:
Cause
problem if the wrong method or property accessed because all the
information about stored value is get resolved only at run time
|
As
source in for
each
iteration:
Not
supported
|
As
source in for
each
iteration:
Supported
|
As
source in for
each
iteration:
Supported
|
Application
Area:
Useful
when doesn't have more information about the data type i.e., to
hold objects as base class.
|
Application
Area:
Useful
when getting result out of the linq queries. In 3.5 framework it
introduce to support linq feature.
|
Application
Area:
Useful
when coding using reflection or dynamic language support or with
the COM objects, because we require to write less amount of code.
|
Compilation
Example:
Object
o = new Button();
o.Width doesn’t compile |
Compilation
Example:
var
o = new Button();
o.Width will compile |
Compilation
Example:
dynamic
o = new Button();
o.Width and even o.xyz() will compile where xyz is not a member |
References:
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