ASP.NET State management

    Whenever page is posted to the server, a new instance of the Web page class is created each time. This means that all information associated with the page and the controls on the page get lost with each round trip.
    To overcome this situation, ASP.NET provides various options to preserve the data. These are known as state management techniques:

Client-Side or Client-based State Management options:
·         View state
·         Control state
·         Hidden fields
·         Cookies
·         Query strings
View state, control state, hidden fields, cookies, and query strings all involve storing data on the client.
Server-side or Server-based State Management options:
·         Application state
·         Session state
·         Profile Properties
             application state, session state, and profile properties all store data in memory on the server.

While dealing with client-based options for state management it stores information either in the page or on the client computer.  Information is not maintained on the server between round trips.

View State

While page processing, the current state of the page and it’s all controls get hashed into a string and then saved in the form of hidden field on the page. If specified value in MaxPageStateFieldLength property get exceeds than the data to be stored then it get stored in multiple hidden fields.  When the page is posted back to the server, the page parses the view-state string at page initialization and restores property information in the page.
The ViewState property provides a dictionary object for retaining values between multiple requests for the same page. This is the default method that the page uses to preserve page and control property values between round trips.
Control State:
In order to persist or preserve the control data we can use control state option. For example,  we have a tab control that needs to be preserve selected tab in between post backs to server we can use control sate option..
We can use ViewState here, but it may possible that at page level ViewState is turned off.
The ControlState property allows you to persist property information that is specific to a control and cannot be turned off like the ViewState property.

Hidden Fields:
  Hiddenfields are also used to store values on page. Hidden file does not render on page. Hiddenfield stores data in it's Value property. To make hiddenfield values available during page precoessing we need to submit the page using HTTP POST method or command. Hiddenfield values are not available using HTTP GET command.

 Cookie is nothing but the small amount of that is stored on client's browser using text file on client's file system on in memory.
Define and set value in cookie:
Response.Cookie["MyValue"].Value = "Test Value";
Get Cookie value

lblCookieText = Request.Cookies["MyValue"].Value;

Query String:
 Using Querystring application passes information or data by appending it to URL using question mark "?" like:"Test Name"&phone="1234";

QueryString provides easy but 'limited' way to pass data from one page to other. To make querystring available during page processing, page must be submitted using HTTP GET command.

Application State:
   Application state provides way be store data which can be acessible globally in application. Application state uses System.Web.ApplicationState class.
    Defining and storing application state:
    Application["Name"] = "My Web";

// Accessing application variable value
string name;
if (Application["Name"] != null)
      name = Application["Name"].ToString();

Session State:
 Session state is way to store data in session variable for the current single browser session. If different users uses application , each users session state will be different.
Session State stroed in below three ways/ Session State Modes:

1. InProc: Means storing session in memory of the web server. It is the defualt session storage. InProc mode is high performant as it get read from same process. But it get affected by Worker process as both are in same process.

2. Stateserver: Storage location is server memeory with a seperate process, and not with the same process with worker process. This is less perfoamant process than InProc but it does not get affected in worker process get affected.

3.SQL Server:  Stores the data in SQL server database.