using the singleton design pattern for managing session state in asp.net

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Introduction

Hello, A few days back I was trying to design and develop a session object(a stand alone class) dealing with asp.net session varibales.The problem I faced was if I create a stand alone class in a project and assigned property’s to it(variables which I wanted to persist) ,and instantiate that class from the global.asax session start event ,this looked pretty fine in the beginning as I was only using these variables in the code behinds, but when I tried accessing these variables from other classes in the application, I couldn’t do it ,because the object was not in the same context (System.Web.HttpContext).So I did some research here and there and decided to use the singleton design patternto solve this problem. If you are new to this pattern you should read this article on msdn .

(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/singletondespatt.asp)

So I created a stand alone class Smart_Session and assigned property methods to it. And a static method which gets the object out of the session and returns it to the caller (both aspx and .cs files).And this class always returns a single instance at any call.

The code below is an example of one such class and can be referred to in code as per the following code:

<P>public class someclass</P>
<P>{
Smart_Session oSession = Smart_Session.GetCurrentSmart_Session();


<P>public string someMethod()
</P>

<P> <P>{
<P> 
<P>oSession.Get_Set_Get_Set_prod_id =007;


<P>}</P>


<P>}
</P>

Example of Smart_Session

 <PRE>public class Smart_Session 

{

private const string SMART_SESSION = "SESGLOBAL";

private bool init;

private string user_name;

private string user_pwd;

private int lang_id;

private int acc_id;

private string purch_id;

private int purch_date;

private int serial_no;

private string prod_id;

private string pkg_id; 

private string err_msg;

private string email_id;

private Smart_Session()

{

Refresh();

}

public void Refresh()

{

this.prod_id = "";

this.serial_no = 0;

this.purch_date = 0;

this.purch_id = "";

this.acc_id = 0;

this.lang_id = 0;

this.pkg_id = null;

this.init = false;

this.err_msg = "";

this.email_id=""; 

}

public string GetSetEmailID

{

get

{

return this.email_id;

}

set

{

this.email_id = value;

}

}

public string GetSetPassword

{

get

{

return this.user_pwd;

}

set

{

this.user_pwd = value;

}

}

public string GetSetUserName

{

get

{

return this.user_name;

}

set

{

this.user_name = value;

}

}

public string Get_Set_prod_id

{

get

{

return this.prod_id;

}

set

{

this.prod_id = value;

}

}

public int Get_Set_serial_no

{

get

{

return this.serial_no;

}

set

{

this.serial_no = value;

}

}

public int Get_Set_purch_date

{

get

{

return this.purch_date;

}

set

{

this.purch_date = value;

}

}

public string Get_Set_purch_id

{

get

{

return this.purch_id;

}

set

{

this.purch_id = value;

}

}

public int Get_Set_acc_id

{

get

{

return this.acc_id;

}

set

{

this.acc_id = value;

}

}

public int Get_Set_lang_id

{

get

{

return this.lang_id;

}

set

{

this.lang_id = value;

}

}

public string Get_Set_pkg_id

{

get 

{

return this.pkg_id;

}

set

{

this.pkg_id=value;

}

}

public string Get_Set_spErrorMsg

{

get 

{

return this.err_msg;

}

set

{

this.err_msg=value;

}

}

public bool init_Status

{

get

{

return this.init;

}

}

public static Smart_Session GetCurrentSmart_Session()

{

Smart_Session oSmart_Session;

{

if (null == System.Web.HttpContext.Current.Session[SMART_SESSION])

{

//No current session object exists, use private constructor to 

// create an instance, place it into the session

oSmart_Session = new Smart_Session();

System.Web.HttpContext.Current.Session[SMART_SESSION] = oSmart_Session;

}

else

{

//Retrieve the already instance that was already created

oSmart_Session = (Smart_Session)System.Web.HttpContext.Current.Session[SMART_SESSION];

}

//Return the single instance of this class that was stored in the session

return oSmart_Session;

}

}

}

Conclusion

There are many advantages to using singleton objects stored in the Session object rather than using individual session keys for storing information. It is useful for objects that are meant to exist for the entire session (grouping logical items, impact analysis, intellisense, etc) and especially for objects that are really only needed for a period of time on a web site until the user completes a particular process (much easier to identify misuse of variables and to conserve resources when the process is completed but the session will continue).