Predefined attributes in c#

Introduction

In this article I am going to discuss few important attributes of C# . There are two types of attribute in C#

1)      User defined attributes

2)      Pre defined attributes

In this article I am going to discuss few very important pre defined attributes. Rather than discuss theory of attributes I will be showing example of them followed by simple introduction of attributes.

What is attributes? 

Let me give informal definition of attribute (Please search in google for bookish definition). Attributes are nothing but some extra information injected with your normal c# code. For example I have written some statement in my code and I want to inform C# compiler how to precede that particular code. So according to attribute value compiler will take decision.

Another more example, I have change something in some existing function and though I have changed it I don’t want to remove it. Now if anyone try to call my old function I will inform then “Hey..One new version has added for same function ..Why not you try it?”. So using attribute we can perform such kind of magic.

Let’s start with example

According to my word , I will show example of few important attributes. Microsoft has given lot of very essential attributes to work with c#. Some of them are

1. STAThread
2. Obsolete
3. Serializable
4. Conditional
5. NonSerialized
6. ThreadStatic

So, In our example we will see one by one with example

STAThread

If we use STAThread attribute in our program, It represents that our program will follow Single thread model in threading concept of C#

The implementation of this attribute is

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Test1
{
    class Program
    {
        [STAThread]  //Single thread model
        static void Main(string[] args)
        {
        }
    }
}
 

MTAThread

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Test1
{
    class Program
    {
        [MTAThread]  //Multi thread model
        static void Main(string[]  args)
        {
        }
    }
}   

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Test1
{
    class Test
    {
        [Obsolete("Please use new function",true)]
        public void OldFunction()
        {
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Test t = new Test();
            t.OldFunction();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Test1
{
    [Serializable]
    class Test
    {
        public void OldFunction()
        {
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
    
        }
    }
}
  
 

NonSerialized

This is exact opposite of Serialized attribute. We can use this attribute anywhere in class(like Serialized) but it ensure that the particular code will not maintain it’s state during Serialization.

using System;
using System.Collections.Generic;
using System.Diagnostics;
namespace Test1
{
    class Test
    {
        [NonSerialized]
        public String Name;
    }
    class Program
    {
        static void Main(string[] args)
        {
            Console.ReadLine();
        }
    }
}
 
 

Conditional

If you start your programming life with C programming then you might aware of conditional compilation feature. Conditional attribute is very similar with it. If we define attribute value in program then the code snippet(here Msg() function] will compile otherwise not. Sample code is in below.

#define EXECUTE_ME
using System;
using System.Collections.Generic;
using System.Diagnostics;
namespace Test1
{
    class Test
    {
        [Conditional("EXECUTE_ME")]
        public static void Msg()
        {
            Console.WriteLine("Hello");
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Test.Msg();
            Console.ReadLine();
        }
    }
}
 

ThreadStatic

Threasstatic attribute is only applicable for static member. It may be static data member or function member. If we use Threadstatic then it ensures that the static field will create for each and every thread separately. Below is sample example of Threadstatic attribute.

using System;
using System.Collections.Generic;
using System.Diagnostics;
namespace Test1
{
    class Test
    {
        [ThreadStatic]
        public static void Print()
        {
         }
        [ThreadStatic]
        public static int Value = 0;
    }
    class Program
    {
        static void Main(string[] args)
        {
            
            Console.ReadLine();
        }
    }
}