Difference between ref and out parameters

ref and out parameters: An Overview

Ref and out parameters are used to pass an argument within a method. Actually, Both parameters indicate that an argument/parameter is passed by reference. By default, parameters are passed to a method by value. By using these keywords we can pass a parameter by reference. In this C# Tutorial, We will explore the ref and out which will include what are ref and out parameters in C#, The difference between ref and out parameters, and when to use ref and out parameters.

Ref

• The ref keyword is used to pass an argument as a reference.
• This means that when the value of that parameter is changed in the method.
• It gets reflected in the calling method.
• An argument that is passed using a ref keyword must be initialized in the calling method before it is passed to the called method.

Out

• The out keyword is also used to pass an argument like the ref keyword.
• But the argument can be passed without assigning any value to it.
• An argument that is passed using an out keyword must be initialized in the called method before it returns back to the calling method.

Program with the ref and out keyword

Let's Elaborate ref and out parameters in C# Compiler with its example:

 public class Example
{
 public static void Main() //calling method
 {
 int val1 = 0; //must be initialized 
 int val2; //optional

 Example1(ref val1);
 Console.WriteLine(val1); // val1=1

 Example2(out val2);
 Console.WriteLine(val2); // val2=2
 }

 static void Example1(ref int value) //called method
 {
 value = 1;
 }
 static void Example2(out int value) //called method
 {
 value = 2; //must be initialized 
 }
}

 

Output

 
1
2
    

Note

1. Do not be confused with the concept of passing by reference and the concept of reference type. These two concepts are not the same.

2. A value type or a reference type can be passed to the method parameter by using the ref keyword. There is no boxing of a value type when it is passed by reference.

3. Properties cannot be passed to ref or out parameters since internally they are functions and not members/variables.

Read More - C Sharp Interview Questions

Ref and out-in method overloading

Both ref and out cannot be used in method overloading simultaneously. However, ref and out are treated differently at run-time but they are treated same at compile time (CLR doesn't differentiates between the two while it created IL for ref and out). Hence methods cannot be overloaded when one method takes a ref parameter and other method takes an out parameter. The following two methods are identical in terms of compilation.

 class MyClass
{
 public void Method(out int a) // compiler error “cannot define overloaded”
 {
 // method that differ only on ref and out"
 }
 public void Method(ref int a) 
 {
 // method that differ only on ref and out" 
 }
} 

However, method overloading can be done, if one method takes a ref or out argument and the other method takes a simple argument. The following example is perfectly valid to be overloaded.

 class MyClass
{
 public void Method(int a) 
 {

 }
 public void Method(out int a)
 {
 // method differ in signature.
 }
}

Ref Vs Out: The Difference

Conclusion:

I hope you will enjoy the ref and out keywords while programming with C#. I would like to have feedback from my blog readers. Your valuable feedback, questions, or comments about this article are always welcome. Also, consider our C# Programming Course for a better understanding of C# concepts.

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