Validation of viewstate MAC failed error in Asp.net

This asp.net tutorial, we will discuss how to resolve the error “Validation of viewstate MAC failed” which sometimes comes in Asp.Net.

Server Error in ‘/’ Application.
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

See http://go.microsoft.com/fwlink/?LinkID=314055 for more information.
Server Error in ‘/’ Application.
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

See http://go.microsoft.com/fwlink/?LinkID=314055 for more information.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

See http://go.microsoft.com/fwlink/?LinkID=314055 for more information.

Source Error:

The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL:

1. Add a “Debug=true” directive at the top of the file that generated the error. Example:

<%@ Page Language="C#" Debug="true" %>

or:

2) Add the following section to the configuration file of your application:

<configuration>
 <system.web>
 <compilation debug="true"/>
 </system.web>
 </configuration>

Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode.

Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario.

Stack Trace:

[ViewStateException: Invalid ViewState.

Validation of viewstate MAC failed

We need to add a machine key in the web.com file.

You can visit this URL and then try to Generate a machine key.

You will get something like this:

<system.web>
<machineKey validationKey="123333333333444444555345136797526EA6" decryptionKey="dddddddddddddddddddddd2AEF6457EE76ADCCB51EF477F87E7F09D8" validation="SHA1" decryption="AES" />
</system.web>

Then Open your web.config file and put the above tag before </system.web>.

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