Difference between is and as operators in C#

1. Difference between is and as operators in C#
S.No Is operator As opeator
1 Meaning: Meaning:
The is operator allows us to The as operator is used to perform
check whether an object is certain types of conversions
compatible with a specific type. between compatible reference
Here the phrase "is types.
compatible" means that an i.e., The as operator is used to
object is either of that type or is perform explicit type conversion of
derived from that type. reference type.If the type being
converted is compatible with the
specified type,then that conversion
is successful else as operator will
return a null value.
2 How it works ? How it works ?
i.Checks whether Object is i.Checks whether Object is
compatible with given type compatible with given type
ii. If yes, returns true ii. If yes, returns not null reference
iii. If no, returns false i.e same object
iii. If no, returns null instead of
Remarks: raising an exception.
An is expression evaluates to
true if both of the following
conditions are met:
expression is not null.
expression can be cast to
type.
That is, a cast expression of
the form (type)(expression) will
complete without throwing an
exception. For more
information, see 7.6.6 Cast
expressions.
3 When to use is operator ? When to use as operator ?
The is-cast is only ideal if the If we need to use the casted
casted variable will not be variable, use the as-cast.
needed for further use.
4 For what type of For what type of conversions,as
conversions,is operator can operator can be used ?
be used ? as operator only performs
is operator only considers reference conversions and boxing
reference conversions, boxing conversions.
conversions, and unboxing
conversions.
5 Syntax: Syntax:

2. expression is type expression as type
6 Example: Example:
int k = 0; object x = "I am here";
if (k is object) object y = 10;
{
Console.WriteLine("i is an string s1 = x as string; // here
object"); conversion is compatible so,s1="I
} am Here"
string s2 = y as string;// here
conversion is imcompatible
so,s2=null
Notes:
1.Syntax: expression as type is equivalent to:
expression is type ? (type)expression : (type)null
Example: Employee e = obj as Employee; is equivalent to:
Employee e = obj is Employee ? (Employee)obj : (Employee)null;
2.Both is and as operators cannot be overloaded.
3.The is operator will never throw an exception.
4. A compile-time warning will be issued if the expression expression is type is known to
always be true or always be false.
5. Both is and as operators cannot use user-defined conversions
6.The as cast is an efficient, elegant way to cast in the C# language. It promotes
exception-neutral and less redundant code.
References:
http://www.dotnetspider.com/sites/961/Forum-1095-What-difference-between-operator-
C.aspx
http://msdn.microsoft.com/en-us/library/scekt9xw%28v=vs.100%29.aspx
http://msdn.microsoft.com/en-us/library/cscsdfbt%28v=vs.80%29.aspx
http://mr-ponna.com/Question/363/What-is-difference-between-is-and-as-operators-in-c-/
http://msdn.microsoft.com/en-us/library/8edha89s.aspx
http://www.c-sharpcorner.com/uploadfile/dhananjaycoder/type-casting-with-is-and-as-
operator-in-C-Sharp/
http://www.c-sharpcorner.com/uploadfile/abhikumarvatsa/the-is-and-as-operators-in-C-
Sharp/
http://www.dotnetperls.com/as

3. http://www.dotnetperls.com/is
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