ASP.Net State Management
We know any web page are state less, means when we post a page to server , server will not return the same state as it was send . The reason is , when we post a form /page to the server , server process the page and generate new html and send to browser .For example a web page is taking student information , student name , date of birth ,country ,state .We enter student name , date of birth , now we have Select student country “Say” India , page need to go server and get state list of India .When it posted to server for state information , the whole html is created again and when comes to browser , student name , date of birth not data is not there .Input fields are empty.
To over come this problem , Asp.Net introduced State Management . State Management is a technique to keep data while post back occur , that means , when student page with student data will be posted to the server , and server will return student page with student data.
There are several way to maintain State in ASP.Net , such as View State ,Hidden Fields ,
Cookies , Query String , Control State . Some are Clint Site and Some are Server Site.
View State : View state is the technique that the ASP.NET page uses to preserve page and control values when post back . The working of View State can be controlled by C# code , by default view state enabled . View state is a hidden filed with serialized into base64-encoded strings.We van enable /disable code from page level
%@ Page Language="C#"
CodeFile="Default2.aspx.cs"
Inherits="Default2" EnableViewState="false"
We can encrypt view state
%@ Page Language="C#"
CodeFile="Default2.aspx.cs"
Inherits="Default2"
EnableViewState="true
ViewStateEncryptionMode="Always"
There is also Option for enable/disable at control level
asp:TextBox EnableViewState=true
We can also do enable/disable the whole page and enable/disable on or more control.
We can also use View State variable as follow
protected void
Page_Load(object sender, EventArgs e)
{
if (ViewState["NameOfStudent"] != null)
txtStudentName.Text = ViewState["NameOfUser"].ToString();
else
txtStudentName.Text = "Not
set yet...";
}
protected void SubmitForm_Click(object
sender, EventArgs e)
{
ViewState["NameOfUser"]
= txtStudentName.Text;
txtStudentName.Text = NameField.Text;
}
We can see view state value , to see the value , please write click on mouse and go to "View source" , here is the example
Hidden field : Hidden field is control , which is not displayed in the front end .This field are use to hold control value , here is an example
<body>
<form
id="form1"
runat="server">
<div>
<asp:HiddenField ID="hiddn_1"
runat="server"
/>
<asp:TextBox ID="txtStudent"
runat="server"
></asp:TextBox>
<asp:Button
ID="Button1"
runat="server"
oncommand="Button1_Command"
Text="Button" />
<br />
</div>
</form>
</body>
public partial
class _Default
: System.Web.UI.Page
{
protected void Page_Load(object
sender, EventArgs e)
{
txtStudent.Text = hiddn_1.Value;
}
protected void Button1_Command(object
sender, CommandEventArgs e)
{
hiddn_1.Value = txtStudent.Text;
}
}
Here , hidden field hold the value of "txtStudent" , while page load , the process is reverse
Cookies : Cookies are small text to stored some value .This is like key pair combination.
Cookies are associated with a Web site, not with a specific page, so the
browser and server will exchange cookie information no matter what page
the user requests from your site.
protected void Page_Load(object sender, EventArgs
e)
{
Response.Cookies["LoggedUsere"].Value
= "MyUser";
Response.Cookies["LoggedUser"].Expires
= DateTime.Now.AddDays(1);
}
protected void Button1_Command(object
sender, CommandEventArgs e)
{
HttpCookie obj = new HttpCookie("LoggedUser");
string loggedUser =
Request.Cookies["LoggedUser"].Values.ToString();
}
Here , user values stored in cookies and later retrieved in a sting.
Context.Handler
Context handler just return the immediate previous web page when Server.transfer occure , this does not works for Response.redirect.
public partial
class MyContext1
: System.Web.UI.Page
{
internal string value
{
get
{
return TextBox1.Text;
}
}
protected void Button1_Click(object
sender, EventArgs e)
{
Server.Transfer("MyContext1.aspx");
}
}
public partial
class MyContext2
: System.Web.UI.Page
{
protected void Page_Load(object
sender, EventArgs e)
{
MyContext1 largePare;
largePare = (MyContext1)Context.Handler;
this.textBox1.Text =
largePare.value;
}
}
Query String
This is popularly used in ASP.Net Application . A string of query can be generated before posting and later while loading field value can be retrive from query .this works for both Server.Transfer and Request.Response.
protected void
Button1_Click(object sender, EventArgs e)
{
Server.Transfer("MyContext1.aspx?mText=20");
}
protected void
Page_Load(object sender, EventArgs e)
{
if (Request.QueryString["mText"] != null)
{
this.Textbox1.Text =
Request.QueryString["mText"].ToString();
}
}
Session State
Asp.net offer a unique key to each user when a new session begin , this is called session id/ Session key.This key is stored is cookie.In each request client send the key to Server .Session State maintained by Globax.aspx
<%@ Application Language="C#" %>
<script runat="server">
void Session_Start(object sender, EventArgs
e)
{
// Code that runs when a new
session is started
Session["MyNumber"]
= 100;
}
void Session_End(object sender, EventArgs
e)
{
// Code that runs when a session
ends.
// Note: The Session_End event is
raised only when the sessionstate mode
// is set to InProc in the
Web.config file. If session mode is set to StateServer
// or SQLServer, the event is not
raised.
}
</script>
Application State
As ASP.Net is stateless protocal ,it is application state which can hold some value , we can use during page load event to show the value to client .Application variable inisialised when application starts only.
<%@ Application Language="C#" %>
<script runat="server">
void Application_Start(object sender, EventArgs
e)
{
// Code that runs on application
startup
Application["MyAppVarable"]
= "100";
}
</script>
Catching
Catching is a technique to deliver the same Web Page which is frequently used without rebuild the page HTML.For I am using page A , after 3 second I called same page A to browser , server will return page A to browse from cache memory.But the question is how many time cache hold the page , which page will hold by cache , there are several caching technique output caching , data catching ,object catching.
