State Management in ASP.NET Core MVC

State Management means to preserve the State of a Control, Web Page, Data, Object or User in application explicitly because all ASP.NET Web Applications are Stateless that is bydefault for each page posted to the Server, the State of Controls is lost.

For Example when a form is submitted in ASP, all form values are cleared,Suppose you have submitted a form with a lot of information and the server comes back with an error , you will have to go back to the form and correct the information ,when you click the Back button and what happens , all form values are cleared and you will have to start all over again. The website did not maintain state of controls , so here we need to store the page values at the time of PostBack we can do it by State Mananagement. Now all Web Applications demand a high level of State Management from control to Application level.

There are two types of State Management techniques listed below:

Client Side State Management : In this technique we manage state of controls at client side following are some Client Side State Management techniques.

• Hidden Field
• View State
• Cookies
• Control State
• Query Strings

Server Side State Management Techniques: In this technique state of controls or users manage at server side following are some state management techniques

• Session State
• Application State

View State Management

View State is one of the most useful Client Side State Management technique. It can store the page values at the time of Post Back of page(Sending and receiving informtion from/to Server). ASP.Net pages provides the View State Property as a built in structure for automaically storing values between multiple request from the same page.

when a form is submitted in ASP, all form values are cleared,Suppose you have submitted a form with a lot of information and the server comes back with an error , you will have to go back to the form and correct the information ,when you click the Back button and what happens , all form values are cleared and you will have to start all over again. The website did not maintain state of controls , so here we need to store the page values at the time of PostBack we can do it by View State Property of Controls .
Client Side State Management does not use any Server Resources, it store information using client side options.

Advantages of View State : following are some advantages of View State.

• Easy to Implement
• No any Server Resources are Required
• Enhanced Security features like it can be Encoded and Comopressed

Disdvantages of View State : following are some Disadvantages of View State.

• There can be some performnace overhead if we are going to store large amount of data.
• It stored view state values in Hidden Field in hashed format still it can be easily trapped.
• It does not have any support on Mobile Devices.

When we should use View State ?
We should use View State

• When size of data is small, because data are bind with page Controls , so for larger amount of data it can be cause of performance overhead.
• When Secure data is not required.

When we should avoid View State ?
We should avoid View State

• When Controls never changes.
• Controls is repopulated on every Post Backs.
• The Control is an input control and it changes only of user Actions.

Where is View State Stored ?
View State stored the value of page controls as a string which is hashed and encoded in some hashing and encoding technology. It only contains information about page and its controls. It does not have any interaction with Server.It stays alongwith the page in the Client Browser. View State use Hidden Field to store its information in a encoded format.
You can see view state values by right click on browser and click view source , you will get the following section of code:-

                
input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE"
  value="2NvUlofSaheYe5BlK1m4Yh65gVDCn2o9F722HH3XvSMqUJWOzcs6F17MOkQ22rlkXxXff/2Ig="
                 
                

Now look at the value, it look likes a encrypted string, this is Base64 encoded string so it can easily be decoded.
Base64 makes a string suitable for HTTP transfer plus it makes it little hard to read.

                
View["xyz"]= 0; Stored 0 in xyz  //means it stores a variable.
View["xyz"]="hello this is Sudhir";  // means it stores the string value.
View[_classObject]=_objectofaClass;  //means it stores the object of a Class 
                

How you can store Object in View State ? We can store an Object easily as we can store String or Integer type variables in View State, we need to Convert it into Stream of Bytes because View State store information in Hidden field in the page , so we need to use Serialization. If Object which are tying to store in View State are not Serializable then we will get an error message.

 
[Serializable]
Public Class ClassName
{
    //Class members goes here
}

                

How to trace View State Information : if you want to trace your View State information , by just enable "Trace" option of page directive.

                
Page Title="" Language="C#" MasterPageFile="~/Sitemaster.Master" Trace="true" 
TraceMode="SortByTime" AutoEventWireup="true" 
CodeBehind="frmTokenGeneration.aspx.cs" Inherits="DigitalToken.Staff.frmTokenGeneration"
                 
                

Now Run your web application , you can view the details of View State size alongwith Control ID in control tree section.

Enable and Disable View State : We can enable and disable view state for a single Control as well as at Page level also. to turn off View State for a single Control , set EnableViewState property of Control to false.

                    
TextBox1.EnableViewState=false;
                    
                

To turnoff the View State of entire page , we need to set EnableViewState to false of page Directive as shown below
Page language="C#" EnableViewState=false;

Session State Management in ASP.NET

A Session is one of the most useful Server Side State Management technique used for store information of web pages. A Session is a Unique Instance of the browser. A Single user can have multiple sessions , by visiting your application with multiple instances of the browser running with a different Session ID on his machine.
Session is Single User Global data.

Session provides facility to store information on Server Memory.It can support any type of Object to store alongwith our own custom objects.
For every Client , Session data is Stored seperately , which means session data is stored on a per Client basis.
As we all know ,HTTP is a Stateless Protocol , it can not hold client information on a page , if user insert some information and move to the next page, that data will be lost and the user would not be able to retrieve that information, so need to store information Session provides these facilities to us.
State Management using Session is one of the best ASP.NET feature because it is Secure, Transparent from Users and we can Store any kind of Object in it.

Advantages of Session : Following are some advantages of Session-

• Session helps to maintain User State and data over the application.
• Session is Easy to implement and we can Store any kind of object in it
• Session Stores data seperately
• Session is Secure and Transparent from the Users.

Disdvantages of Session : Following are some Disadvantages of Session,

• Performance overhead in case of large volume of data/user , because Session data is stored in Server Memory and Clients read data from the Server.
• Overhead involved in Serialization and Deserialization of Session data because in the case of State Server and Sql Server modes, we need to Serialize the Objects before storing them.

Session Events: There are two types of Session Events avialble in ASP.NET.

• Session_Start
• Session_End

• Session.Remove(sessionvariable name is here) : It removes an item from the Session State Collection.
• Session.RemoveAll() :- Removes all items from the Session Collection.
• Session.Clear() :- Remove all items from session collection .there is no difference between Clear and RemoveAll methos
• Session.Abandon() :- Cancels the Current Session.