Csharp/CSharp Tutorial/Attribute/Obsolete Attribute

Demonstrate the Obsolete attribute.

using System; 
 
class MainClass { 
 
  [Obsolete("Use myMeth2, instead.")]  
  static int myMethod(int a, int b) { 
    return 0; 
  } 
 
  // Improved version of myMethod. 
  static int myMethod2(int a, int b) { 
    return 1; 
  } 
 
  public static void Main() { 
   // warning displayed for this 
    Console.WriteLine("4 / 3 is " + myMethod(4, 3)); 
 
   // no warning here 
    Console.WriteLine("4 / 3 is " + myMethod2(4, 3));  
  } 
}

4 / 3 is 0
4 / 3 is 1

Obsolete attribute: throw an error if the user tries to use Method2

using System;
class MainClass
{
  
  [Obsolete("Method2 has been replaced by NewMethod2", true)]
  public static int Method2()
  {
    return 2;
  }
  public static void Main() 
  {
    Console.WriteLine(Method2());
  }
}

ObsoleteattributethrowanerroriftheusertriestouseMethod2.cs(16,21): error CS0619:
        "MainClass.Method2()" is obsolete: "Method2 has been replaced by NewMethod2"

Obsolete attribute: warn the user that Method is obsolete

using System;
class MainClass
{
  
  [Obsolete("Method1 has been replaced by NewMethod1", false)]
  public static int Method1()
  {
    return 1;
  }
  public static void Main() 
  {
    Console.WriteLine(Method1());

  }
}

ObsoleteattributewarntheuserthatMethodisobsolete.cs(18,21): warning CS0618: "MainClass.Method1()" is
        obsolete: "Method1 has been replaced by NewMethod1"
1

The Obsolete Attribute

1. The Obsolete attribute is short for System.ObsoleteAttribute
2. The Obsolete attribute lets you mark a program element as obsolete.

It has this general form:

[Obsolete("message")]

Using ObsoleteAttribute

using System;
class Program
{
  public static void Main()
  {
      ObsoleteMethod();
  }
  [Obsolete]
  public static void ObsoleteMethod()
  {
  }
}