(A) Ref Keyword
- 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.
- Both the function definition and function calling must explicitly use the ref keyword.
- In function call argument passed to a ref parameter must first be initialized.
- ref parameter variable should not be declare as a constant variable.
- 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:
(B) Out Keyword
- 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.
- Both the function definition and function calling must explicitly use the out keyword.
- It is not necessary to initialize out parameter variable that is pass in function call.
- out parameter variable should not be declare as a constant variable.
- 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:
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.
