Explore State Management

Session[“firstName”] = “Gaurav”	//User’s first name
Session[“lastName”] = “Arora”	//User’s last name

// Clear the session variable 
Session[“FirstName”] = null; 

//Clear all Session variables 
Session.Abandon();  

object errorData;
 //Load errorData from errors.xml 

 CacheDependency fileDependency = 
     new CacheDependency(Server.MapPath("errors.xml")); 
 Cache.Insert("ERROR_INFO", errorData, fileDependency);

(b) Time based expiration :

Allows to invalidate a specific cache item depending on predefined time.

//Absolute Expiration

Cache.Insert("EMP_NAME", "Shubhabrata", null, 
             DateTime.Now.AddDays(1), Cache.NoSlidingExpiration);

//Sliding Expiration

Cache.Insert("EMP_NAME", "Shubhabrata", null, 
             Cache.NoAbsoluteExpiration, TimeSpan.FromSeconds(60));

(c) Key dependency :

Allows to invalidate a specific cache item depending when another cache item changes.

string[] relatedKeys = new string[1]; 
relatedKeys[0] = "EMP_NUM";
CacheDependency keyDependency = new CacheDependency(null, relatedKeys); 
Cache["EMP_NUM"] = 5435;
Cache.Insert("EMP_NAME", "Shubhabrata", keyDependency);
Cache.Insert("EMP_ADDR", "Bhubaneswar", keyDependency);
Cache.Insert("EMP_SAL", "5555USD", keyDependency);

.NET remoting

You might be thinking how .NET remoting can be used for data caching?

The same question came to my mind when I heard about it for the first time. As you know the .NET remoting singleton object shares the same instance with multiple clients so singleton objects can be used to store and share data between different client invocations. Since .NET remoting can be used outside the process and machine, this option is very useful when we want to cache data and share it across servers and users particularly in a web farm scenario. In this approach we can store the data as member variables of singleton remoting object and provide methods to read and save data. But while implementing this we need to ensure that the remoting object used as cache is not destroyed by the garbage collector. For that we will have to set the remoting cache object's lease period to infinite so that the lease period never times out. We can do that by overriding the InitializeLifetimeService method of MarshalByRefObject and return null from this method. But the only issue with this approach is performance. As the analysis says the performance is very poor in this approach when compared to other approaches. Anyway it is up to the application designers/developers to analyze different options and use the best one that suits the requirement.

Memory-mapped files

You all know what a memory-mapped file is. It is basically about mapping a file on disk to a specific range of addresses in the application's process address space. This option allows different processes to use the same data by increasing the application performance. As using memory-mapped file is not very popular among .NET developers, I would personally not suggest this approach as implementing this involves a lot of complexities and also .NET Framework doesn't support this. But if anyone is very much interested in using this approach then they will have to develop their own custom solution as per their own requirement.

Static variables

We use static variables for storing data or objects globally so that it can be accessed during the life of the application. Similarly, in ASP.NET we can use static objects for caching data and we can also provide methods to retrieve and save data to the cache. As static variables are stored in the process area, performance wise it is faster. But since it is very difficult to implement expiration policies and dependencies incase of static variables, I generally prefer ASP.NET cache object over this option. Another problem is that the custom static cache object has to be thread-safe which has to be implemented carefully.

Example:

public class CustomCache
{
    //Synchronized to implement thread-safe

    static Hashtable _myCache = 
             Hashtable.Synchronized(new Hashtable());
    
    public static object GetData(object key)
    {
        return _myCache[key];
    }
    
    public static void SetData(object key, object val)
    {
        _myCache[key] = val;
    }
}

II. Client-Side State Management

Cookies

Cookie is a very familiar term in web development environment. Cookie is a client-side storage that is sent to the server for each request and also received as response back from the server. Because of its size limitation (4096 bytes) it should be used for storing small amount of data. Expiration policies can be set for cookies to invalidate the items after a certain period of time. The following example shows how Cookie can be used in an ASP.NET application:

protected void Page_Load(object sender, EventArgs e) 
{
    if (this.ViewState["MY_NAME"] == null) 
    { 
        this.ViewState["MY_NAME"] = "Shuby";
    } 
    
    //txtName is a TextBox control 

    this.txtName.Text = this.ViewState["MY_NAME"].ToString(); 
}

string authorid;
authorid=Request.Params[“authorid”];

Note: You can only use HTTP-Get method to post the web page, or you will never get the value from query strings.