System.Web.UI.ViewStateException ,Invalid viewstate

Question

My website is throwing the below exceptions everyday and i couldn't find the solution. i did few research in web and this is what i do so far. adding below option to aspx won't solve the problem.

ValidateRequest="false" EnableEventValidation="false" ViewStateEncryptionMode="Never" EnableViewStateMac="false"

Also, my Referral Url is the correct URL and i have no idea how it redirect with two (same) parameters. there is no such link in my referral page. Please help.

ERROR LOG

URL : http://www.abcd.com/company-details.aspx?com=asia-pacific-pte-ltd&com=asia-pacific-pte-ltd

referral URL : http://www.abcd.com/companies/asia-pacific-pte-ltd/

Inner Exception Type: System.Web.UI.ViewStateException

Inner Exception: Invalid viewstate. Client IP: 192.162.19.193 Port: 1966 User-Agent: Opera/9.80 (Windows NT 6.1; WOW64; MRA 6.0 (build 6001)) Presto/2.12.388 Version/12.11 ViewState: 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...

Inner Source: 

Exception Type: System.Web.HttpException

Exception: The state information is invalid for this page and might be corrupted.

Stack Trace: at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError) 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.ProcessRequest(HttpContext context) at ASP.exhibition_details_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework64\v2.0.50727\Temporary ASP.NET Files\root\0f461847\442b0502\App_Web_bfjqxdef.20.cs:line 0 at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

UPDATE i have fixed the error by compressing the ViewState from below link http://www.codeproject.com/Articles/14733/ViewState-Compression

and fixed the Invalid length for a Base-64 char array error by replacing the original method with this.

protected override object LoadPageStateFromPersistenceMedium()
    {
        string viewState = Request.Form["__VSTATE"];
        viewState = viewState.Replace(" ", "+");

        int mod4 = viewState.Length % 4;
        if (mod4 > 0)
        {
            viewState += new string('=', 4 - mod4);
        }
        byte[] bytes = Convert.FromBase64String(viewState);
        bytes = Compressor.Decompress(bytes);
        LosFormatter formatter = new LosFormatter();
        return formatter.Deserialize(Convert.ToBase64String(bytes));
    }

Thanks everyone for help :)

Answer 1

I am sorry that say that but your site did not have anything worng, and you need to re-enable your EventValidations as soon as possible.

What you see is an attempt to hack your site by sending many test numbers with your ViewState trying to find your hash key.

The IP you give have a big list of activity the last few days.

Now, alternative what may cause this error is the breaking of the ViewState. You can compress it and split it if you have too big ViewState. You can also disable all the controls that not needed. Also you can add a log to see from inside what's is going on right on a base page.