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home / developersection / interviews / difference between ref and out keywords in c#
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Niraj Kumar Mishra
Niraj Kumar Mishra

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Niraj Kumar Mishra
Niraj Kumar Mishra 28 Aug 2017
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ref and out both allow the called method to modify a parameter. The difference between them is what happens before you make the call.

  • ref means that the parameter has a value on it before going into the function. 

  • out means that the parameter has no official value before going into the function. 

Example:
using System;
public class Example
{
   public static void Main() //calling method
   {
       int val1 = 0; //must be initialized 
       int val2; //optional
       Example1(ref val1);
       Console.WriteLine("Result of Ref keywordis=>"+val1);// val1=1
       Example2(out val2);
       Console.WriteLine("Result of out keywordis=>"+val2);// val2=2
       Console.ReadKey();
   }
 
   static void Example1(ref int value) //called method
   {
       value = 1;
   }
   static void Example2(out int value) //called method
   {
       value = 2; //must be initialized 
   }
}
then it produce the following result:
Niraj Kumar Mishra
if you not initialize the val1 with any value then your code not compile.
Error:Use of unassigned local variable 'val1'





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