What Is The Difference Between ViewState and Session?
ViewState and Session are both state management mechanisms in ASP.NET, but they serve different purposes and have different scopes. Here are the key differences between ViewState and Session:
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Scope:
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ViewState: ViewState is used to maintain the state of controls on a single web page. It is stored as a hidden field within the page and is used to preserve the state between postbacks for that specific page.
- Session: Session is used to maintain user-specific data across multiple requests and pages. It is stored on the server and associated with a user's session, identified by a session ID. Session data is available across different pages within the same session.
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Storage Location:
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ViewState: ViewState is stored within the HTML output as a hidden field and is transmitted between the client and the server with each postback. It is stored on the client side.
- Session: Session data is stored on the server, typically in memory, but it can also be stored in other storage mediums like a database or external session state providers.
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Accessibility:
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ViewState: ViewState is accessible only within the same web page. It is used to maintain the state of controls on that particular page.
- Session: Session data is accessible across multiple pages within the same session. It can be accessed and modified from different pages within the application.
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Content and Size:
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ViewState: ViewState stores the state of controls, including their values, properties, and other relevant information, to preserve their state across postbacks. It can contain a significant amount of data, depending on the complexity of the page and the controls on it.
- Session: Session data can store any type of serializable data, such as user preferences, shopping cart items, or user authentication information. Session data can be more extensive and versatile than ViewState.
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Lifespan:
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ViewState: ViewState exists only for the lifetime of a single web page. It is created during page rendering, transmitted to the client, and restored on subsequent postbacks for that specific page. When the user navigates away from the page or the session ends, the ViewState is discarded.
- Session: Session data persists throughout a user's session, which is typically determined by factors such as session timeout or explicit session termination. Session data is maintained until the session ends or the data is explicitly cleared.
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Security:
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ViewState: ViewState can be tampered with by users, as it resides on the client side. To enhance ViewState security, ViewState MAC (Message Authentication Code) and ViewState encryption can be enabled to detect tampering attempts and protect sensitive data within ViewState.
- Session: Session data is stored on the server, making it less prone to tampering or unauthorized access from the client side. However, proper security measures should still be implemented to protect session data, such as using secure session IDs and implementing appropriate access controls.
In summary, ViewState is used to maintain the state of controls within a single web page, while Session is used to maintain user-specific data across multiple pages and requests within a session. ViewState is stored on the client side and has a limited scope, while Session data is stored on the server and is accessible across multiple pages.