State Management is a process of maintaining the state of the control or variable after page postback from server or between pages. In Asp.Net we are having many ways to maintain the state management. Basically it is dividied into server side and client side state management. Depends on the resource that we have to plan. They are as follows....
1. Session state
2. Hidden Variables
3. Query String
4. Cookies
5. ViewState
6. Caching
Out of which session state and caching are server side state management. others are client side state management.
1. Session StateSession State is responsible for maintaining the state of a variable between pages and page postback. There are two types of session state. They are
a. Application state
b. Session state
An object that is instant in application state will be available to the entire application. The lifetime of that instance will be available as long as application exists. Synatax for it is
Application.lock();
Application["Name"] = "Senthil";
Application.unlock();
string strName = Application["Name"].ToString();
and an instance created in session state will be available for that session (i.e browser).
Session["RoleID"] = "ADMIN";
string strRole = Session["RoleID"].ToString();
Session state can stored in three places
a. InProc - same system
b. StateServer - storing values in other server. Use " net start aspnet_state" for configuring the state server.
c. SQLServer - In database - use "aspnet_regsql" for configuring the sql server.
This can be set in web.config
<configuration> <system.web> <sessionstate mode="InProc" stateserver="129.23.33.53" sqlserver="" cookieless="true" /> </system.web></configuration>
To get more info about state management, set the trace to on
<configuration> <system.web> <trace enable="true" pageoutput="true" />
</system.web>
If pageoutput is set to false, then we find the contents in trace.axd file which is available in the root folder.
2. Hidden variables
Hidden controls are for storing few informations and retrieving it when page gets submits. We cannot get one hidden value in another page. The syntax for hidden variables are as follows.
<input type="hidden" name="hid" value="">
<%=Request.Form("hid")%>
3. QueryString
Easiest way to transfer data between pages is the querystring. But we cannot transfer a bulk of data through it. Basically querystring has two keywords ? and &.
Example
document.frm.action="login.aspx?Name=" & strName & "?Role=ADMIN"
<%= Request.QueryString["Name"] %>
4. Cookies
Cookies are client side and it is used to store few values in the client machine. We cannot create cookies in server side. Many browsers restrict using cookies in the websites. The class that supports cookies in dotnet are HttpCookies.
5. ViewState
ViewState are used to maintain the state of the control. It can be set page wise or control wise. To set it by page wise
<% @ Page EnableviewState="True" %>
For setting viewstate control wise set the viewstate property to true.
The value of the control would be retained once the pages get postback.
6. Caching
Caching too places a part in state management. Its similar to session state but the only difference is we have to set the duration for it.
Caching can be done by page levels or application levels.
Syntax for page level caching[CODE]
<% outputcache duration="10" valuebyParam="none" />[CODE]
