Click here to Skip to main content
Click here to Skip to main content

Weird Error: Unable to Validate Data in ASP.NET website

, 8 Nov 2009
Rate this:
Please Sign up or sign in to vote.
A weird error that comes when a page is opened for a long time and then posted back

Have you ever come across a situation where your website which was working for the last couple of months gives a weird error "Unable to Validate Data". Yesterday, while working I found that my website which is already published in IIS throws this error. Initially I thought the error might be with my code, but I found that everything is good with the code. So I looked forward to internet and found that this error comes when the viewstate of a page cannot be decrypted when the response is received from the client.

When I looked at where the error was occurring (Target Site) I found:

Unable to validate data at
System.Web.Configuration.MachineKey.GetDecodedData(Byte[] buf, Byte[] modifier,
Int32 start, Int32 length, Int32& dataLength) at
System.Web.UI.LosFormatter.Deserialize(String input) 

Actually the problem is with the viewstate. The viewstate is actually decrypted in the server using a secret Machine key which resides on the server. The interesting thing is the key gets regenerated after a certain time. Therefore when the user returns the viewstate, if the machine identified key is changed, the decryption of viewstate fails and thus throws this nasty error.

Solution

The solution is simple. First of all, to solve the issue, I disabled the ViewState for the current page by putting EnableViewState = false. I even disabled this for the entire viewstate for the website using Web.config. But still the error.
Finally I used "EnableViewStateMac =false" in pages section. Voila, this cures the problem.

<pages buffer="true" enableViewStateMac="flase"/>
</pages>

Just place the following between the system.web section and the site starts working.

Another solution that you might use as well is to place the machine key directly on your web.config, so that it always decrypts and encrypts using the static key values. To do this, you need to use the following:

<machinekey validationkey="22E995276703B846C4AD0881EE3159FFCB376CD48B27F64
9A074815C83D5C925038938F6943555687582CBC186DB22E552FCDB4D46
124BAADEE85A857CC135BC" decryptionkey="60588EB661A6483348C20F92659775872CB06427AF20733C" 
validation="SHA1"></machinekey>

You might use this site to Generate your validation key as well.
To get deep knowledge on what makes this happen, I found some insight from the Internet and read some articles of MSDN. Let us talk a little on that note.
Say you made a request for a page in the server. After you place the request the server processes it, encrypts the viewstate that the server receives using the encryption mentioned. Basically it uses the key mentioned in the Machine.config to encrypt the viewstate data. Finally it converts to Base64 and embeds into some hidden fields.

We can mention the machine key in Web.config too so that it uses it for the current website. You might use the AutoGenerate option too to enable/disable autogeneration of key during runtime.

Your comments are welcome.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Abhishek Sur
Architect
India India
Did you like his post?
 
Oh, lets go a bit further to know him better.
Visit his Website : www.abhisheksur.com to know more about Abhishek.
 
Abhishek also authored a book on .NET 4.5 Features and recommends you to read it, you will learn a lot from it.
http://bit.ly/EXPERTCookBook
 
Basically he is from India, who loves to explore the .NET world. He loves to code and in his leisure you always find him talking about technical stuffs.
 
Presently he is working in WPF, a new foundation to UI development, but mostly he likes to work on architecture and business classes. ASP.NET is one of his strength as well.
Have any problem? Write to him in his Forum.
 
You can also mail him directly to abhi2434@yahoo.com
 
Want a Coder like him for your project?
Drop him a mail to contact@abhisheksur.com
 
Visit His Blog

Dotnet Tricks and Tips



Dont forget to vote or share your comments about his Writing
Follow on   Twitter   Google+

Comments and Discussions

 
QuestionThanks for the explanation PinmemberVC Sekhar Parepalli21-Nov-13 13:57 
AnswerRe: Thanks for the explanation PinmemberVC Sekhar Parepalli22-Nov-13 5:56 
QuestionMachineCode in web.config Pinmemberankeshjain198926-Aug-13 19:49 
AnswerRe: MachineCode in web.config PinprofessionalAbhishek Sur27-Aug-13 1:07 
GeneralRe: MachineCode in web.config Pinmemberankeshjain198931-Aug-13 2:53 
GeneralMy vote of 4 Pinmemberstuy29-Oct-12 13:14 
GeneralGood Work Pinmemberranjan_namitaputra13-Nov-09 8:30 
GeneralNote PinmemberSourav_9i13-Nov-09 0:11 
GeneralThank you! Pinmemberdlcodeproject9-Nov-09 4:22 
GeneralRe: Thank you! PinmemberAbhishek Sur9-Nov-09 8:38 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web02 | 2.8.140721.1 | Last Updated 8 Nov 2009
Article Copyright 2009 by Abhishek Sur
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid