title: Invalid Viewstate, Invalid length for a Base-64 char array or string
body: <p>I face this error from time to time, </p>
  
  <blockquote>
    <p>ExecuteStep at line:0 at Column:0 The state information is invalid for this page and might be corrupted. (*)Invalid viewstate</p>
  </blockquote>
  
  <p>Inner exception:</p>
  
  <blockquote>
    <p>unhandled exception in Application_Error
    At Load at line:0 at Column:0 Invalid length for a Base-64 char array or string</p>
  </blockquote>
  
  <p>debugging is enabled, and the pdb file exists, and as you see the debug info does not exactly tell me where it happened.</p>
  
  <p>I'm using ASP.NET, C#, DotNet 4.5</p>
  
  <p>this only occurs on a specific page's load.</p>
  
  <pre><code>[FormatException: Invalid length for a Base-64 char array or string.]
     System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength) +10545359
     System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength) +130
     System.Convert.FromBase64String(String s) +41
     System.Web.UI.ObjectStateFormatter.Deserialize(String inputString, Purpose purpose) +66
     System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter2.Deserialize(String serializedState, Purpose purpose) +8
     System.Web.UI.Util.DeserializeWithAssert(IStateFormatter2 formatter, String serializedState, Purpose purpose) +40
     System.Web.UI.HiddenFieldPageStatePersister.Load() +127
  
  [ViewStateException: Invalid viewstate. 
      Client IP: ::1
      Port: 
      Referer: http://localhost:8000/ERP/MemberArea/Permits/Process_New.aspx
      Path: /ERP/MemberArea/Permits/Process_New.aspx
      User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
      ViewState: 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...]
  
  [HttpException (0x80004005): The state information is invalid for this page and might be corrupted.]
     System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) +198
     System.Web.UI.HiddenFieldPageStatePersister.Load() +266
     System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +88
     System.Web.UI.Page.LoadAllState() +36
     System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6704
     System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +245
     System.Web.UI.Page.ProcessRequest() +72
     System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) +21
     System.Web.UI.Page.ProcessRequest(HttpContext context) +58
     ASP.memberarea_permits_process_new_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\ERP\5da93c6f\27d5fbc5\App_Web_llo4zgw1.4.cs:0
     System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +341
     System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously) +69
  </code></pre>