Introduction
In ASP.NET applications, you may encounter an error message stating "Validation of viewstate MAC failed." This error typically indicates a session timeout. This article will guide you through the process of using a state server to store the session, which helps to resolve this issue.
Problem
Error message: Validation of viewstate MAC failed.
Cause
This error occurs when the ViewState data fails to be decrypted during a postback, commonly due to a session timeout.
Solution
To resolve this issue, configure your application to use a state server for session management. The state server stores the session data on a separate server, ensuring that the data remains available even if the application restarts or the user's session times out.
Follow these steps to configure the state server:
1. Locate your application's web.config file.
2. Add or modify the sessionState element inside the <system.web> section, as shown in the example below:
<configuration>
<system.web>
<sessionState mode="StateServer"
stateConnectionString="tcpip=127.0.0.1:42424"
cookieless="false"
timeout="20"/>
</system.web>
</configuration>
3. Set the "cookieless" attribute to "false" to use cookies for session tracking.
4. Set the "timeout" attribute to the desired number of minutes for session expiration (e.g., "20" minutes).
Conclusion
By configuring your ASP.NET application to use a state server for session management, you can resolve the "Validation of viewstate MAC failed" error. This will ensure a more stable user experience and prevent session timeouts from causing issues with ViewState data.
