Csharp/CSharp Tutorial/Language Basics/Parameter Value

Passing ref-types by value

<source lang="csharp">using System; class Person {

 public string fullName;
 public int age;
 public Person(string n, int a)
 {
   fullName = n;
   age = a;
 }
 public void PrintInfo()
 {
   Console.WriteLine("{0} is {1} years old", fullName, age);
 }

} class MainClass {

 public static void SendAPersonByValue(Person p)
 {
   p.age = 99;
   p = new Person("TOM", 999);
 }
 public static void Main() 
 {
   Person fred = new Person("Fred", 12);
   fred.PrintInfo();
   SendAPersonByValue(fred);
   fred.PrintInfo();
 }

}</source>

Fred is 12 years old
Fred is 99 years old

Value types are passed by value

<source lang="csharp">using System;

class Test {

 /* This method causes no change to the arguments used in the call. */ 
 public void noChange(int i, int j) { 
   i = i + j; 
   j = -j; 
 } 

}

class MainClass {

 public static void Main() { 
   Test ob = new Test(); 

   int a = 15, b = 20; 

   Console.WriteLine("a and b before call: " + 
                      a + " " + b); 

   ob.noChange(a, b);  

   Console.WriteLine("a and b after call: " + 
                      a + " " + b); 
 } 

}</source>

a and b before call: 15 20
a and b after call: 15 20