title: Invalid viewstate error in asp.net page
body: <p>The webpage is a simple registration type page. Each user has to fill around 200 fields. There is 1 parent table and 6 child tables. Each table info is displayed in separate AJAX tab panel and details gets saved on each tab navigation. I have hosted the website in intranet and concurrently the details were entered by 100 users. Initially everything went on well and entries were getting saved in the database but after sometime the AJAX loading image was displayed and the website appeared to be very slow. Details of users did not get saved in database. Finally Firefox browser crashed for some people and for some the application did not even get logged out also. The website hanged!
  I reset IIS also and everything went on for few minutes and the same problem started again!
  I have used NHibernate framework, AJAX, ASP.Net 4.0 as front end and SQL server 2008 as back end. </p>
  
  <p>The following are the error details in the log file:</p>
  
  <pre><code>    2014-08-11 10:05:40,953 [22] INFO ASP.global_asax servername :  - 
  ************************* 11/08/2014 10:05 **************************** IP Address: xx.x.xxx.xx Exception Type: System.Web.HttpException Exception: Request timed out. Source: 
  **************************************************************************
  
      2014-08-11 10:05:40,984 [39] INFO ASP.global_asax servername :  - 
      ************************* 11/08/2014 10:05 ****************************`
      IP Address: xx.x.xxx.xx
      Exception Type: System.Web.HttpException
      Exception: The client disconnected.
      Source: System.Web
      Stack Trace: 
         at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError)
         at System.Web.UI.ViewStateException.ThrowViewStateError(Exception inner, String persistedState)
         at System.Web.UI.ClientScriptManager.EnsureEventValidationFieldLoaded()
         at System.Web.UI.ClientScriptManager.ValidateEvent(String uniqueId, String argument)
         at System.Web.UI.Control.ValidateEvent(String uniqueID, String eventArgument)
         at System.Web.UI.WebControls.DropDownList.LoadPostData(String postDataKey, NameValueCollection postCollection)
         at System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.LoadPostData(String postDataKey, NameValueCollection postCollection)
         at System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean fBeforeLoad)
         at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
         at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
         at System.Web.UI.Page.ProcessRequest()
         at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
         at System.Web.UI.Page.ProcessRequest(HttpContext context)
         at ASP.ui_shape_profilereg_aspx.ProcessRequest(HttpContext context)
         at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
         at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously)
  
          **************************************************************************
  
      Inner Exception Type: System.Web.UI.ViewStateException
      Inner Exception: Invalid viewstate. 
          Client IP: xx.x.xx.xx
          Port: 44853
          Referer: mypageurl.aspx
          Path: /xx/xxxx/xxxxx.aspx
          User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20100101 Firefox/17.0
          ViewState: /wEW4xwCvIuN0AIC1tvizQkCq67tpAgC76DRtAcCx+CW8AkCub6h1gwCgL6h1gwC2tGLOAKy2oaCCQLvkqjEDgKhnYMvArnixL8OApuuotUNAvL6+LQMAr6MpOoPArqKsKgDAvHcqZUKAqz10osPAu71uZENAqOa+OUDAtH844kHApLejoMIApLe0pAOAqze2pAOAqze0pAOAqu34bMNAtGFvd4JAq3e2pAOAq3e0pAOAtKFvd4JAqu3pa0NAtGF4dsJAsyRw5MHAsyRu9kFAqu35bMNAtGFod4JAsyRx5MHAsyRv9kFAof0kuQOApj0kuQOAoibuIoCAo/tyqYKAvnF+KIIAunaxagHAuu0gK8OAr+m5s0MAp3r6bkJAp/A0coMAs+s/tsNAseN/JQOApaT7OIDAr/1vroLArWhqYQMAqDH34kLArCo9ecHAsuo0fkHAtCo0fkHAqa0zecNApe1zIMOAofa5u0CApja5u0CApna5u0CApra5u0CApva5u0CApza5u0CAp3a5u0CAp7a5u0CApbxu6IGAoaekcwKApmekcwKApiekcwKApuekcwKApqekcwKAp2ekcwKApyekcwKAp+ekcwKAo6ekcwKAoGekcwKApme0c8KApme3c8KApme2c8KApme5c8KApme4c8KApme7c8KApme6c8KApme9c8KApmescwKApmevcwKApie0c8KApie3c8KApie2c8KApie5c8KApie4c8KApie7c8KApie6c8KApie9c8KApie...
      Inner Source: 
      **************************************************************************
  
      `2014-08-11 10:05:54,875 [82] INFO ASP.global_asax servername :  - 
      ************************* 11/08/2014 10:05 ****************************
      IP Address: xx.x.xxx.xx
      Exception Type: System.Web.HttpException
      Exception: Request timed out.
      Source: 
  
      **************************************************************************
  </code></pre>
  
  <p>These errors are repeatedly found in logs.</p>
  
  <p>I have tried increasing the database size but have not tested after that. </p>
  
  <p>I am completely stuck! Please guide how to proceed.</p>