State Management Techniques in ASP.NET-1

This article discusses various options for state management for web applications developed using ASP.NET. Generally, web applications are based on stateless HTTP protocol which does not retain any information about user requests. In typical client and server communication using HTTP protocol, page is created each time the page is requested.

Developer is forced to implement various state management techniques when developing applications which provide customized content and which "remembers" the user.
Here we are here with various options for ASP.NET developer to implement state management techniques in their applications. Broadly, we can classify state management techniques as client side state management or server side state management. Each technique has its own pros and cons. Let's start with exploring client side state management options.
Client side State management Options:

ASP.NET provides various client side state management options like Cookies, QueryStrings (URL), Hidden fields, View State and Control state (ASP.NET 2.0). Let's discuss each of client side state management options.
Bandwidth should be considered while implementing client side state management options because they involve in each roundtrip to server. Example: Cookies are exchanged between client and server for each page request.
Cookie:

A cookie is a small piece of text stored on user's computer. Usually, information is stored as name-value pairs. Cookies are used by websites to keep track of visitors. Every time a user visits a website, cookies are retrieved from user machine and help identify the user.

Let's see an example which makes use of cookies to customize web page.

if (Request.Cookies["UserId"] != null)
lbMessage.text = "Dear" + Request.Cookies["UserId"].Value + ", Welcome to our website!";
else
lbMessage.text = "Guest,welcome to our website!";
If you want to store client's information use the below code
Response.Cookies["UserId"].Value=username;
Advantages:
• Simplicity
Disadvantages:
• Cookies can be disabled on user browsers
• Cookies are transmitted for each HTTP request/response causing overhead on bandwidth
• Inappropriate for sensitive data
Hidden fields:

Hidden fields are used to store data at the page level. As its name says, these fields are not rendered by the browser. It's just like a standard control for which you can set its properties. Whenever a page is submitted to server, hidden fields values are also posted to server along with other controls on the page. Now that all the asp.net web controls have built in state management in the form of view state and new feature in asp.net 2.0 control state, hidden fields functionality seems to be redundant. We can still use it to store insignificant data. We can use hidden fields in ASP.NET pages using following syntax
protected System.Web.UI.HtmlControls.HtmlInputHidden Hidden1;

//to assign a value to Hidden field
Hidden1.Value="Create hidden fields";
//to retrieve a value
string str=Hidden1.Value;
Advantages:
• Simple to implement for a page specific data
• Can store small amount of data so they take less size.
Disadvantages:
• Inappropriate for sensitive data
• Hidden field values can be intercepted(clearly visible) when passed over a network
View State:

View State can be used to store state information for a single user. View State is a built in feature in web controls to persist data between page post backs. You can set View State on/off for each control using EnableViewState property. By default, EnableViewState property will be set to true. View state mechanism poses performance overhead. View state information of all the controls on the page will be submitted to server on each post back. To reduce performance penalty, disable View State for all the controls for which you don't need state. (Data grid usually doesn't need to maintain state). You can also disable View State for the entire page by adding EnableViewState=false to @page directive. View state data is encoded as binary Base64 - encoded which add approximately 30% overhead. Care must be taken to ensure view state for a page is smaller in size. View State can be used using following syntax in an ASP.NET web page.
// Add item to ViewState
ViewState["myviewstate"] = myValue;

//Reading items from ViewState
Response.Write(ViewState["myviewstate"]);

Advantages:
• Simple for page level data
• Encrypted
• Can be set at the control level
Disadvantages:
• Overhead in encoding View State values
• Makes a page heavy
Query strings:
Query strings are usually used to send information from one page to another page. They are passed along with URL in clear text. Now that cross page posting feature is back in asp.net 2.0, Query strings seem to be redundant. Most browsers impose a limit of 255 characters on URL length. We can only pass smaller amounts of data using query strings. Since Query strings are sent in clear text, we can also encrypt query values. Also, keep in mind that characters that are not valid in a URL must be encoded using Server.UrlEncode.
Let's assume that we have a Data Grid with a list of products, and a hyperlink in the grid that goes to a product detail page, it would be an ideal use of the Query String to include the product ID in the Query String of the link to the product details page (for example, productdetails.aspx?productid=4).
When product details page is being requested, the product information can be obtained by using the following codes:
string productid;
productid=Request.Params["productid"];
Advantages:
• Simple to Implement
Disadvantages:
• Human Readable
• Client browser limit on URL length
• Cross paging functionality makes it redundant
• Easily modified by end user


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