There are various causes for this error, this is one we had some time ago when paginating through a DataGrid (for this case we’re talking about ASP.NET 1.1); the error appeared systematically under a specific user pattern:
Invalid length for a Base-64 char array. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.FormatException: Invalid length for a Base-64 char array. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [FormatException: Invalid length for a Base-64 char array.] System.Convert.FromBase64String(String s) +0 System.Web.UI.LosFormatter.Deserialize(String input) +25 System.Web.UI.Page.LoadPageStateFromPersistenceMedium() +101 [HttpException (0x80004005): Invalid_Viewstate Client IP: 213.199.128.155 Port: 24949 User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.0.04506; .NET CLR 1.1.4322; InfoPath.2; MS-RTC LM 8) ViewState: dDw2Mjg2Njc3OTM7dDw7bDxpPDA+Oz47bDx0PDtsPGk8MT47aTwzPjs+O2w8dDxwPHA8bDxUZXh0Oz47bDxcZTs+Pjs+Ozs+O3Q8QDA8cDxwP Gw8V2ViR3JpZF9Tb3J0RXhwcmVzc2lvbjtTaG93Rm9vdGVyO1Zpc2libGU7XyFTQjtQYWdlQ291bnQ7UGFnZVNpemU7V2ViR3JpZF9MYWJlbHM7 V2ViR3JpZF9Dc3NDbGFzc0J1dHRvbnM7Q3NzQ2xhc3M7XyFJdGVtQ291bnQ7XyFEYXRhU291cmNlSXRlbUNvdW50O1dlYkdyaWRfU29ydFR5cGU7 V2ViR3JpZF9Dc3NDbGFzcztEYXRhS2V5czs+O2w8TnVtZXJvO288Zj47bzx0PjtpPDI+O2k8MT47aTwxMD47YjxBQUVBQUFELy8vLy9BUUFBQUFBQ 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We tried to use the ViewState Decoder and got the same error. During a discussion with the customer we found he was using an HttpModule to have a sort of custom logging to trace all incoming requests and outgoing responses… during the same discussion we browsed a few other working pages on the same site and doing some tests we found a difference in the viewstate produced.
To make the story short we notice a weird character sequence in the failing viewstates (="") while in the working viewstates we never have two double-quote characters like that. Again using ViewState Decoder we tried to past the same failing viewstate but we changed the two last digits with two “equal” signs (==) and it worked…
This meant that something was touching the viewstate, and after some further investigation we found a problem in the custom HttpModule which under some circumstances was incorrectly adding the two double-quotes at the end of the string. Needless to say that fixing the bug also resolved the problem.
End of the story: if you search the Internet you can find a few viewstate decoders and loggers tools, give them a try if you find yourself in trouble with the viewstate, with some luck you’ll be able to quickly spot the problem and fix it. Of course, if this is not enough you can still call CSS
Carlo
I discovered that if I URLEncode the ViewState value, it solved my problem
In my case, there was a space character in the encrypted string. I replaced the space character with a '+' . It solved the problem.
byte[] cipherBytes = Convert.FromBase64String(cipherText.Replace(' ','+'));
I was having a similar problem, by changing the code to Convert.FromBase64String(cipherText.Replace(' ','+'));
Works great.
Thanks a lot.
I was having exactly the same problem, works great by changing the code to Convert.FromBase64String(cipherText.Replace(' ','+'));
Is it only space having this issue or some characters too? Just asking to be sure.
Seems quite tricky to me, i am having the same issue, I try this and update when it is solved. Thanks for sharing such amazing way to resolve this bug :)
After urlDecode processes the text, it replaces all '+' chars with ' ' ... thus the error. You should simply call this statement to make it base 64 compatible again:
sEncryptedString = sEncryptedString.Replace(' ', '+');