Validation of viewstate MAC failed

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.

[HttpException (0x80004005): Unable to validate data.]

   System.Web.Configuration.MachineKeySection.GetDecodedData(Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Int32& dataLength) +294

   System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) +203

[ViewStateException: Invalid viewstate.

        Client IP: 218.28.26.86

        Port: 45262

        User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; FDM)

        ViewState: 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...]

[HttpException (0x80004005): 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.]

   System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) +267

   System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) +282

   System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) +4

   System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState) +37

   System.Web.UI.HiddenFieldPageStatePersister.Load() +198

   System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +83

   System.Web.UI.Page.LoadAllState() +35

   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +7350

   System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +213

   System.Web.UI.Page.ProcessRequest() +86

   System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) +18

   System.Web.UI.Page.ProcessRequest(HttpContext context) +49

   ASP.admin_articleadd_aspx.ProcessRequest(HttpContext context) +4

   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +358

   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64