Session State

A Session State Example

public class Furniture

{
    public string Name;
    public string Description;
    public decimal Cost;

    public Furniture(string name, string description,
      decimal cost)
    {
        Name = name;
        Description = description;
        Cost = cost;
    }
}

public partial class SessionStateExample : System.Web.UI.Page
{
 protected void Page_Load(Object sender, EventArgs e)
 {
 if (!this.IsPostBack)
 {
 // Create Furniture objects.
 Furniture piece1 = new Furniture("Econo Sofa",
 "Acme Inc.", 74.99M);
 Furniture piece2 = new Furniture("Pioneer Table",

 "Heritage Unit", 866.75M);
 Furniture piece3 = new Furniture("Retro Cabinet",
 "Sixties Ltd.", 300.11M);

 // Add objects to session state.
 Session["Furniture1"] = piece1;
 Session["Furniture2"] = piece2;
 Session["Furniture3"] = piece3;

 // Add rows to list control.
 lstItems.Items.Add(piece1.Name);
 lstItems.Items.Add(piece2.Name);
 lstItems.Items.Add(piece3.Name);
 }

 // Display some basic information about the session.
 // This is useful for testing configuration settings.
 lblSession.Text = "Session ID: " + Session.SessionID;
 lblSession.Text += " Number of Objects: ";
 lblSession.Text += Session.Count.ToString();
 lblSession.Text += " Mode: " + Session.Mode.ToString();
 lblSession.Text += " Is Cookieless: ";
 lblSession.Text += Session.IsCookieless.ToString();
 lblSession.Text += " Is New: ";
 lblSession.Text += Session.IsNewSession.ToString();
 lblSession.Text += " Timeout (minutes): ";
 lblSession.Text += Session.Timeout.ToString();
 }

 protected void cmdMoreInfo_Click(Object sender, EventArgs e)
 {
 if (lstItems.SelectedIndex == -1)
 {
 lblRecord.Text = "No item selected.";
 }
 else
 {
 // Construct the right key name based on the index.
 string key = "Furniture" +
 (lstItems.SelectedIndex + 1).ToString();

 // Retrieve the Furniture object from session state.
 Furniture piece = (Furniture)Session[key];

 // Display the information for this object.
 lblRecord.Text = "Name: " + piece.Name;
 lblRecord.Text += " Manufacturer: ";
 lblRecord.Text += piece.Description;
 lblRecord.Text += " Cost: " + piece.Cost.ToString("c");
 }
 }

}

Session State Configuration

The following listing shows the most important op tions that you can set for the <sessionState>

element. Keep in mind that you won’ t use all of these details at the same time. Some settings apply only to certain session state modes, as you’ll see shortly.

<?xml version="1.0" ?>

Mode

InProc

InProc is the default mode, and it makes the most sense for small websites.

Off

This setting disables session state management for every page in the application. This can provide a slight performance improvement for websit es that are not using session state.

StateServer

With this setting, ASP.NET will use a separate Windows service for state management. This service runs on the same web server, but it’s outside the main ASP.NET process, which gives it a basic level of protection if the ASP.NET process needs to be restarte d. The cost is the increased time delay imposed when state information is transferred between two processes. If you frequently access and change state information, this can make for a fairly unwelcome slowdown.

When using the StateServer setting, you need to specify a value for the stateConnectionString setting. This string identifies the TCP/IP address of the computer that is running the StateServer service and its port number (which is defined by ASP.NET and doesn’t usually n eed to be changed). This allows you to host the StateServer on another computer. If you don’t change this setting, the local server will be used (set as address 127.0.0.1).

SQLServer

This setting instructs ASP.NET to use an SQL Server da tabase to store session information, as identified by the sqlConnectionString attribute. This is the most re silient state store but also the slowest by far. To use this method of state management, you’ll need to have a server with SQL Server installed.

When setting the sqlConnectionString attribute, you follow the same sort of pattern you use with ADO.NET data access. Generally, you’ll need to specify a data source (the server address) and a user ID and password, unless you’re using SQL integrated security.

Here’s a command that creates the session storage database on the current computer, using the default database name ASPState:

aspnet_regsql.exe -S localhost -E –ssadd

Custom

When using custom mode, you need to indicate which session state store provider to use by supplying the customProvider attribute.

Compression

When you set enableCompression to true, session data is compressed before it’s passed out of process. The enableCompression setting only has an effect when you’re using out-of-process session state storage, because it’s only in this situation that the data is serialized.

Application State

Application state allows you to store global objects that can be accessed by any client. Application state is based on the System.Web.HttpApplicationState class, which is provided in all web pages through the built-in Application object.

Application state is similar to session state. It supports the same type of objects, retains information on the server, and uses the same dictionary-based syntax. A common example with application state is a global counter that tracks how many times an operation has been performed by all the web application’s clients.

For example, you could create a global.asax event ha ndler that tracks how many sessions have been created or how many requests have been received into the application. Or you can use similar logic in the Page.Load event handler to track how many times a given page has been requested by various clients. Here’s an example of the latter:

protected void Page_Load(Object sender, EventArgs e)
{
    // Retrieve the current counter value.
    int count = 0;
    if (Application["HitCounterForOrderPage"] != null)
    {
        count = (int)Application["HitCounterForOrderPage"];
    }

    // Increment the counter.
    count++;

    // Store the current counter value.
    Application["HitCounterForOrderPage"] = count;
    lblCounter.Text = count.ToString();
}

Application state isn’t often used, because it’s gen erally inefficient. In the previous example, the counter would probably not keep an accurate count, partic ularly in times of heavy traffic.

To prevent this problem, you need to use the Lo ck() and Unlock() methods, which explicitly allow only one client to access the Application state collection at a time.

To prevent this problem, you need to use the Lo ck() and Unlock() methods, which explicitly allow only

one client to access the Application state collection at a time.
protected void Page_Load(Object sender, EventArgs e)
{
    // Acquire exclusive access.
    Application.Lock();

    int count = 0;
    if (Application["HitCounterForOrderPage"] != null)
    {
        count = (int)Application["HitCounterForOrderPage"];
    }
    count++;
    Application["HitCounterForOrderPage"]=count;
    //Releaseexclusiveaccess.
    Application.Unlock();
    lblCounter.Text=count.ToString();
}

posted on 2012-04-12 16:57 JasonBie 阅读(249) 评论(0) 编辑收藏举报

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