Ref and Out keywords are use for same purpose but there are difference is ref variable cannot use without initialization but out variable use without initialization.
(A) Ref Keyword
1.
When a parameter
pass with ref keyword in function then function work with same
variable value that is passed in function call. If variable value change then
function parameter value also change.
2.
Both the function
definition and function calling must explicitly use the ref keyword.
3.
In function call
argument passed to a ref parameter must first be initialized.
4.
ref parameter variable
should not be declare as a constant variable.
5.
It is not
compulsory that ref parameter name should be same in both
function definition and function call.
Illustration with
an Example
using System;
class Program
{
static void Add(ref int val)
{
val += 12;
Console.WriteLine("Number in Method : {0}", val);
}
static void Main(string[]
args)
{
int
number = 13;
Console.WriteLine("Number before Method call:{0}",number);
Add(ref
number);
Console.WriteLine("Number after Method call:{0}",number);
Console.Read();
}
}
Output:
![]()
![ref keyword]( "output of ref keyword example")
![ref keyword]( "output of ref keyword example")
Number
before Method call:13
Number
in Method : 25
Number
after Method call:25
(B) Out Keyword
1.
When a parameter
pass with out keyword in function then function work with same
variable value that is passed in function call. If variable value change then
function parameter value also change.
2.
Both the function
definition and function calling must explicitly use the out keyword.
3.
It is not
necessary to initialize out parameter variable that is pass in
function call.
4.
out parameter variable
should not be declare as a constant variable.
5.
It is not compulsory
that out parameter name should be same in both function
definition and function call.
Illustration with
an Example
using System;
class Program
{
static void Add(out int val)
{
val = 12;
val += 13;
Console.WriteLine("Number in Method call:{0}",val);
}
static void Main(string[]
args)
{
int
number;
Add(out
number);
Console.WriteLine("Number after Method Call:{0}",number);
Console.Read();
}
}
Output:
Number
in Method call :25
Number
after Method Call:25
Although the ref and out keywords cause different run-time
behaviour, they are not considered part of the method signature at compile
time. Therefore, methods cannot be overloaded if the only difference is that
one method takes a ref argument and the other takes an out argument.