What is view state in ASP.NET?

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View state is where data is used to preserve page values and control values of Web Forms during postback event handling. Data can be stored as hidden fields on the client web page.

In ASP.NET, the view state is a client-side state management technique used to persist the state of a web page across postbacks. When a web form is submitted to the server and a response is sent back to the client, the view state ensures that the state of the controls on the page is maintained, including their property values.

Here’s a breakdown of key points about view state:

  1. State Persistence: View state maintains the state of the controls between round trips to the server. This means that when a user interacts with the page and causes a postback (such as clicking a button), the page is recreated on the server and sent back to the client, but the state of the controls is preserved.
  2. Hidden Field: View state is stored as a hidden field on the page. This hidden field contains serialized data representing the state of the controls. It is sent to the server along with the form data when a postback occurs.
  3. Control State: View state is different from control state. Control state is a subset of view state and is used to persist the state of controls that require it for proper functioning, even if view state is disabled for the page.
  4. Client-Side: View state is maintained on the client-side, meaning it consumes some bandwidth to transmit data back and forth between the client and server. While it helps in maintaining state, excessive use of view state can increase the size of the page, impacting performance.
  5. Security Considerations: Since view state is sent back and forth between the client and server, it can potentially expose sensitive data if not properly secured. ASP.NET provides mechanisms such as encryption and validation to secure view state data.

In an interview setting, it’s good to mention these key points to demonstrate a comprehensive understanding of view state in ASP.NET. Additionally, discussing scenarios where view state might be beneficial or where it might be better to disable or minimize its usage can showcase a deeper understanding of the topic.