The session data is backed by a cache and considered ephemeral data—the site should continue to function without the session data. NET Core maintains session state by providing a cookie to the client that contains a session ID, which is sent to the app with each request.
The app uses the session ID to fetch the session data. A session might not be restricted to a single user—the next user might continue to browse the app with the same session cookie. Session package, which is included in the Microsoft.
App metapackage , provides middleware for managing session state. To enable the session middleware, Startup must contain:. For more information, see Middleware Ordering. Http namespace add a using Microsoft. Http; statement to gain access to the extension methods when the Microsoft. Extensions package is referenced by the project. Both packages are included in the Microsoft.
App metapackage. Keep String and Peek string methods can be used to examine the data without deletion at the end of the request. TempData is particularly useful for redirection when data is required for more than a single request. TempData is implemented by TempData providers using either cookies or session state. Refreshing the page displays TempData["Message"]. Because the cookie is chunked, the single cookie size limit found in ASP. NET Core 1. Most web clients such as web browsers enforce limits on the maximum size of each cookie, the total number of cookies, or both.
If targeting. Session package to the project. In addition to unintended sharing, including data in query strings can create opportunities for Cross-Site Request Forgery CSRF attacks, which can trick users into visiting malicious sites while authenticated.
Attackers can then steal user data from the app or take malicious actions on behalf of the user. Any preserved app or session state must protect against CSRF attacks.
In the following example, middleware adds isVerified to the Items collection. For middleware that's only used by a single app, string keys are acceptable. Middleware shared between app instances should use unique object keys to avoid key collisions. Be careful not to cache user-specific data that may be retrieved by other users' requests.
Use Dependency Injection to make data available to all users:. Define a service containing the data. For example, a class named MyAppData is defined:. This is usually caused by failing to configure at least one IDistributedCache implementation. In the event that the session middleware fails to persist a session for example, if the backing store isn't available , the middleware logs the exception and the request continues normally.
This leads to unpredictable behavior. CommitAsync ; from app code when the app is done writing to the session. LoadAsync throws under the same conditions where the data store is unavailable. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy.
Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Session and state management in ASP. View or download sample code how to download State management State can be stored using several approaches. Each approach is described later in this topic. May include data stored using server-side app code. Session state Session state is an ASP. The cookie session ID: Is sent to the app with each request.
Is used by the app to fetch the session data. Session state exhibits the following behaviors: The session cookie is specific to the browser.
Sessions aren't shared across browsers. Session cookies are deleted when the browser session ends. If a cookie is received for an expired session, a new session is created that uses the same session cookie. Empty sessions aren't retained.
The session must have at least one value set to persist the session across requests. When a session isn't retained, a new session ID is generated for each new request. The app retains a session for a limited time after the last request. The app either sets the session timeout or uses the default value of 20 minutes. Session state is ideal for storing user data: That's specific to a particular session.
Where the data doesn't require permanent storage across sessions. Session data is deleted either when the ISession. Clear implementation is called or when the session expires. There's no default mechanism to inform app code that a client browser has been closed or when the session cookie is deleted or expired on the client. Session state cookies aren't marked essential by default. Session state isn't functional unless tracking is permitted by the site visitor.
Warning Don't store sensitive data in session state. Note Most web clients such as web browsers enforce limits on the maximum size of each cookie, the total number of cookies, or both.
Important If targeting. Is this page helpful? We can also store other objects in session. The following example shows how to store a DataSet in session. NET uses an bit identifier to track each session. This is secure enough and can't be reverse engineered. When a client communicates with a server, only the session ID is transmitted between them. When the client requests for data, ASP. NET looks for the session ID and retrieves the corresponding data.
This is done in the following steps:. For every session state, there is a Session Provider. The following diagram will show you how they are related:.
We can choose the session state provider based on which session state we are selecting. When ASP. NET requests for information based on the session ID, the session state and its corresponding provider are responsible for sending the proper information. The following table shows the session mode along with the provider name:. Apart from that, there is another mode Off.
If we select this option, the session will be disabled for the application. But our objective is to use session, so we will look into the above four session state modes. Session state essentially means all the settings that you have made for your web application for maintaining the session.
Session State itself is a big thing. It says all about your session configuration, either in the web. In the web. I have discussed about each and every section of the connection string. Before I discuss Session Mode, take a brief overview of session events.
You can handle both these events in the global. I have already discussed about session modes in ASP. Following are the different types of session modes available in ASP. For this, we need to configure web. This is the default session mode in ASP.
Its stores session information in the current Application Domain. This is the best session mode for web application performance. But the main disadvantage is that, it will lose data if we restart the server. There are some more advantages and disadvantages of the InProc session mode. I will come to those points later on. As I have already discussed, in InProc mode, session data will be stored on the current application domain. So it is easily and quickly available.
InProc session mode stores its session data in a memory object on the application domain. This is handled by a worker process in the application pool. So if we restart the server, we will lose the session data. If the client request for data, the state provider read the data from an in-memory object and returns it to the client. In web. The above session timeout setting keeps the session alive for 30 minute.
This is configurable from the code-behind too. There are two types of session events available in ASP. This event is called after the session timeout period is over. The general flow for the InProc session state is like this:.
This is a very fast mechanism because no serialization occurs for storing and retrieving data, and data stays inside the same application domain. InProc is the default session mode. It can be very helpful for a small web site and where the number of users is very less. Although InProc session is the fastest, common, and default mechanism, it has a lot of limitations:. As per the above discussion, we can conclude that InProc is a very fast session storing mechanism but suitable only for small web applications.
InProc session data will get lost if we restart the server, or if the application domain is recycled. It is also not suitable for Web Farm and Web Garden scenarios. Now we will have a look the other options available to overcome these problems.
First comes the StateServer mode. This is also called Out-Proc session mode. This server may run on the same system, but it's outside of the main application domain where your web application is running.
This means if you restart your ASP. NET process, your session data will still be alive. This approaches has several disadvantages due to the overhead of the serialization and de-serialization involved, it also increases the cost of data access because every time the user retrieves session data, our application hits a different process. This process is run as a Windows Service. You can start this service from the Windows MMC or from the command prompt. NET state service is set to Manual; we have to set it to Automatic.
By default, this service listens to TCP port , but we can change the port from the Registry editor as show in the picture below:. Now have a look at the web. For the StateServer setting, we need to specify the stateConnectionString. This will identify the system that is running the state server. By default, stateConnectionString used the IP When we are using StateServer, we can configure the stateNetworkTimeOut attribute to specify the maximum number of seconds to wait for the service to respond before canceling the request.
The default timeout value is 10 seconds. For using StateServer, the object which we are going to store should be serialized, and at the time of retrieving, we need to de-serialize it back. I have described this below with an example. We use the StateServer session mode to avoid unnecessary session data loss when restarting our web server. This process maintains all the session data. But we need to serialize the data before storing it in StateServer session mode. As shown in the above figure, when the client sends a request to the web server, the web server stores the session data on the state server.
The StateServer may be the current system or a different system. But it will be totally independent of IIS. The destination of the StateServer will depend on the web. It is not ideal for a developer to change anything in the view state. This is because it should be handled by ASP. Net only. You can store any number of key-value pairs in the Session object.
So on any page, you can store a value in the Session object via the below line of code. This allows the value to be retrieved at a later point in time. To retrieve a value, you can simply issue the below statement. In our example, we are going to use the Session object to store the name entered in the name textbox field in the page. We are then going to retrieve that value and display it on the page accordingly. From the output, you can see that the Session value of name was retrieved and displayed in the browser.
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