Attributes in c#

Hi........

I am doing a work in c# and define Attributes. How can we use attributes in c# and define its properties?

class BasicAttributeDemo
{
    [Obsolete]
    public void MyFirstdeprecatedMethod()
    {
        Console.WriteLine("Called MyFirstdeprecatedMethod().");
    }

    [ObsoleteAttribute]
    public void MySecondDeprecatedMethod()
    {
        Console.WriteLine("Called MySecondDeprecatedMethod().");
    }
In this code define [Obsolete ] what is the meaning of this variable?

On the second part of your question, the System.ObsoleteAttribute is used to mark program elements which should no longer be used.

This is quite common in large class libraries such as the .NET Framework where types or their members may be obsoleted from time to time when better ways of doing the same thing are introduced but the library writer doesn't want to stop existing code from working altogether.

When you attempt to compile a program using obsolete elements, you will usually get a compiler warning that this is the case and suggest you use a different element instead.

However, if the attribute's IsError property is set to true, then the compiler will treat the usage of the obsolete element as an error rather than just a warning.

Here's an example program using a slightly modified version of your own class.

Notice the warnings that you get when you build the program. However, it still runs fine.

Notice also that if you just use 'Obsolete' the compiler automatically replaces it with 'ObsoleteAttribute':

using System;

class BasicAttributeDemo

{

[Obsolete]

public void MyFirstDeprecatedMethod()

{

Console.WriteLine("Called MyFirstDeprecatedMethod().");

}

[ObsoleteAttribute("Use MyThirdMethod instead")]

public void MySecondDeprecatedMethod()

{

Console.WriteLine("Called MySecondDeprecatedMethod().");

}

public void MyThirdMethod()

{

Console.WriteLine("Called MyThirdMethod().");

}

class Test

{

static void Main()

{

var bad = new BasicAttributeDemo();

bad.MyFirstDeprecatedMethod();

bad.MySecondDeprecatedMethod();

bad.MyThirdMethod();

Console.ReadKey();

}

2 Replies

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Vulpes14y ago
On the second part of your question, the System.ObsoleteAttribute is used to mark program elements which should no longer be used.

This is quite common in large class libraries such as the .NET Framework where types or their members may be obsoleted from time to time when better ways of doing the same thing are introduced but the library writer doesn't want to stop existing code from working altogether.

When you attempt to compile a program using obsolete elements, you will usually get a compiler warning that this is the case and suggest you use a different element instead.

However, if the attribute's IsError property is set to true, then the compiler will treat the usage of the obsolete element as an error rather than just a warning.

Here's an example program using a slightly modified version of your own class.

Notice the warnings that you get when you build the program. However, it still runs fine.

Notice also that if you just use 'Obsolete' the compiler automatically replaces it with 'ObsoleteAttribute':

using System;

class BasicAttributeDemo
{
[Obsolete]
public void MyFirstDeprecatedMethod()
{
Console.WriteLine("Called MyFirstDeprecatedMethod().");
}

[ObsoleteAttribute("Use MyThirdMethod instead")]
public void MySecondDeprecatedMethod()
{
Console.WriteLine("Called MySecondDeprecatedMethod().");
}

public void MyThirdMethod()
{
Console.WriteLine("Called MyThirdMethod().");
}

}

class Test
{
static void Main()
{
var bad = new BasicAttributeDemo();
bad.MyFirstDeprecatedMethod();
bad.MySecondDeprecatedMethod();
bad.MyThirdMethod();
Console.ReadKey();
}
}
Satyapriya Nayak14y ago
Hi Aaron,

Please refer Our recommended articles

http://www.c-sharpcorner.com/UploadFile/rajaduraip/AttributesInCS11142005000622AM/AttributesInCS.aspx

Thanks