what is view stat in asp.net?explain with examples.

pooja thorat

13y2kVisual Basic .NET

what is view stat in asp.net? why it is used?explain with examples

2 Replies

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Abhay Shanker13y ago
ViewState is used to maintain the state of controls during page postback and if we save any control values or anything in viewstate we can access those values throughout the page whenever it required for Here is a simple example of using the ViewState to carry values between postbacks

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
ViewState

Name retrieved from ViewState:

______________________________________
using System.Web;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if(ViewState["NameOfUser"] != null)
NameLabel.Text = ViewState["NameOfUser"].ToString();
else
NameLabel.Text = "Not set yet...";
}

protected void SubmitForm_Click(object sender, EventArgs e)
{
ViewState["NameOfUser"] = NameField.Text;
NameLabel.Text = NameField.Text;
}
}

View state is simply text. It is an aggregate of values of controls on a page. It's a string that contains values of page controls hashed and encoded in some manner. The view state contains no information about the server or the client. It only comprises information about the page itself and its controls. It lives along with the page in the user's browser.
As a rule, view state is stored right in the page and therefore it travels with it back and forth. Remember good old hidden input fields? View state is nothing more than a hidden input which holds a hash of control values. If you view the source of an ASP.NET web form you will see something like this:
value="CEbzzzEnmmz+Bc8IDFlnpgCLJ/HB00...>
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Satyapriya Nayak13y ago
The View State is client state mechanism in the ASP.Net statement management.

The view state is control it will be used to maintain the state of the control across the posted back to the server. The value will be stored in the hidden control. Every time it needs to encryption and decryption (serialize and deserialize across the post backs).

The view state can be enabled by setting the property called EnableViewState="true/false". It can be set in the machine config/ web config/ page directives/ control level.

By default it is false. You can enable it by setting boolean flag.

This can be used with in the page and not across the page.

Viewstate["Version"] = txtVersionName.Text.ToString();

The view state also can store the data using the key and value combination. The data will be serialized and stored in the hidden control You can view the source code page and find the hidden control with _viewstate.

Drawbacks:
- Increase the page payload (when you have grid with many rows then every thing has to be loaded and retain again with serialize and deserilize)
- Additional overhead while serialize and deserialize.
- Increase the memory allocation on the server.

protected void Button1_Click(object sender, System.EventArgs e)
    {
        ViewState["FavoriteColor"] = TextBox1.Text.ToString();
        ViewState["City"] = TextBox2.Text.ToString();
        Label1.Text = "Your data saved in ViewState.";
    }
    protected void Button2_Click(object sender, System.EventArgs e)
    {
        string color = (string)ViewState["FavoriteColor"];
        string city = (string)ViewState["City"];

        Label1.Text = "Hi your favorite color is: " + color +
                "
and you came from: " + city;
    }

Please refer the below link

http://msdn.microsoft.com/en-us/library/ms972976.aspx

http://www.codeproject.com/Articles/31344/Beginner-s-Guide-To-View-State
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