asp.net Invalid character in a Base-64 string

Question

I have a c# mobile site and have a problem with some of mobile clients. I have posted a trace below but basically browser of phone or wap gateway that phone connects to internet url encodes viewstate hidden input in the form.

/wEPDwULLTExNTMyOTcwOTBkGAEFBlBtTGlzdA9nZA==

becomes

%2FwEPDwULLTExNTMyOTcwOTBkGAEFBlBtTGlzdA9nZA%3D%3D

so viewstate fails.

Is there anyway to override and urldecode viewstate info before proccessing?

System.Web.HttpException: The state information is invalid for this page and might be corrupted. ---> System.Web.UI.ViewStateException: Invalid viewstate. 
 Client IP: 65.91.116.34
 Port: 37172
 User-Agent: SCH-R430 UP.Browser/6.2.3.8 (GUI) MMP/2.0
 ViewState: %2FwEPDwULLTExNTMyOTcwOTBkGAEFBlBtTGlzdA9nZA%3D%3D
 Referer: 
 Path: /mobile/Inbox.aspx ---> System.FormatException: Invalid character in a Base-64 string.
   at System.Convert.FromBase64String(String s)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
   at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)
   at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
   at System.Web.UI.HiddenFieldPageStatePersister.Load()
   --- End of inner exception stack trace ---
   --- End of inner exception 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.HiddenFieldPageStatePersister.Load()
   at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()
   at System.Web.UI.Page.LoadAllState()
   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.mobile_inbox_aspx.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

(deleted my answer as I didn't spot the "viewstate" bit) – Marc Gravell Oct 16 '09 at 21:14 — Marc Gravell, Oct 16 '09 at 21:14

Justin Grant · Accepted Answer · 2012-03-04T19:19:26.923

You can implement a custom ViewStatePersister object which handles this. You probably want to derive it from HiddenFieldPageStatePersister. Take a look at this article which shows how to implement compression on top of ViewState, but is very similar to what you need to do.

There's a little bit of hackiness involved: you'll need to use reflection to set a field of the StateFormatter base class which is, contrary to what the MSDN docs say, not marked as virtual so can't be overridden without reflection.

score -1 · Answer 2 · answered Dec 11 '15 at 19:25

-1

Use below solution and check if it works. It works for me. Add this code in your asp.net code behind which is causing the issue. Below code is in vb.net

Protected Overrides Function LoadPageStateFromPersistenceMedium() As Object
        Return Session("_ViewState")
    End Function
Protected Overrides Sub SavePageStateToPersistenceMedium(viewState As Object)
        Session("_ViewState") = viewState
    End Sub

answered Dec 11 '15 at 19:25

Nilesh

1

You need to provide code in the programming language the question asks, *not* the programming language of your choice. – AStopher Dec 11 '15 at 19:47

asp.net Invalid character in a Base-64 string

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