Csharp/CSharp Tutorial/Language Basics/Parameter Value

Passing ref-types by value

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();
  }
}

Fred is 12 years old
Fred is 99 years old

Value types are passed by value

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); 
  } 
}

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