What causing this Invalid length for a Base-64 char array

Question

I have very little to go on here  I can t reproduce this locally  but when users get the error I get an automatic email exception notification   Invalid length for a Base-64 char array     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     I m inclined to think there is a problem with data that is being assigned to viewstate  For example   List lt int gt  SelectedActionIDList   GetSelectedActionIDList    ViewState   SelectedActionIDList     SelectedActionIDList    It s difficult to guess the source of the error without being able to reproduce the error locally   If anyone has had any experience with this error  I would really like to know what you found out

User · Answer

As others have mentioned this can be caused when some firewalls and proxies prevent access to pages containing a large amount of ViewState data.

ASP.NET 2.0 introduced the ViewState Chunking mechanism which breaks the ViewState up into manageable chunks, allowing the ViewState to pass through the proxy / firewall without issue.

To enable this feature simply add the following line to your web.config file.

<pages maxPageStateFieldLength="4000">

This should not be used as an alternative to reducing your ViewState size but it can be an effective backstop against the "Invalid length for a Base-64 char array" error resulting from aggressive proxies and the like.

User · Answer

During initial testing for Membership ValidateUser with a SqlMembershipProvider  I use a hash  SHA1  algorithm combined with a salt  and  if I changed the salt length to a length not divisible by four  I received this error   I have not tried any of the fixes above  but if the salt is being altered  this may help someone pinpoint that as the source of this particular error

User · Answer

This isn t an answer  sadly  After running into the intermittent error for some time and finally being annoyed enough to try to fix it  I have yet to find a fix  I have  however  determined a recipe for reproducing my problem  which might help others   In my case it is SOLELY a localhost problem  on my dev machine that also has the app s DB  It s a  NET 2 0 app I m editing with VS2005  The Win7 64 bit machine also has VS2008 and  NET 3 5 installed   Here s what will generate the error  from a variety of forms    Load a fresh copy of the form  Enter some data  and or postback with any of the form s controls  As long as there is no significant delay  repeat all you like  and no errors occur  Wait a little while  1 or 2 minutes maybe  not more than 5   and try another postback    A minute or two delay  waiting for localhost  and then  Connection was reset  by the browser  and global asax s application error trap logs   Application Error event  Invalid length for a Base-64 char array  Stack Trace       at System Convert FromBase64String String s       at System Web UI ObjectStateFormatter Deserialize String inputString       at System Web UI Util DeserializeWithAssert IStateFormatter formatter  String serializedState       at System Web UI HiddenFieldPageStatePersister Load     In this case  it is not the SIZE of the viewstate  but something to do with page and or viewstate caching that seems to be biting me  Setting  lt pages gt  parameters enableEventValidation  false   and viewStateEncryption  Never  in the Web config did not change the behavior  Neither did setting the maxPageStateFieldLength to something modest

User · Answer

Try this   public string EncodeBase64 string data        string s   data Trim   Replace                if  s Length   4  gt  0          s   s PadRight s Length   4 - s Length   4            return Encoding UTF8 GetString Convert FromBase64String s

User · Answer

int len   qs Length   4              if  len  gt  0  qs   qs PadRight qs Length    4 - len           where qs is any base64 encoded string

User · Answer

Take a look at your HttpHandlers  I ve been noticing some weird and completely random errors over the past few months after I implemented a compression tool  RadCompression from Telerik   I was noticing errors like    System Web HttpException  Unable to validate data  System Web HttpException  The client disconnected ---  System Web UI ViewStateException  Invalid viewstate    and   System FormatException  Invalid length for a Base-64 char array  System Web HttpException  The client disconnected  ---  System Web UI ViewStateException  Invalid viewstate    I wrote about this on my blog

User · Answer

As Jon Skeet said  the string must be multiple of 4 bytes  But I was still getting the error   At least it got removed in debug mode  Put a break point on Convert FromBase64String   then step through the code  Miraculously  the error disappeared for me    It is probably related to View states and similar other issues as others have reported

User · Answer

I ve seen this error caused by the combination of good sized viewstate and over aggressive content-filtering devices firewalls  especially when dealing with K-12 Educational institutions     We worked around it by storing Viewstate in SQL Server  Before going that route  I would recommend trying to limit your use of viewstate by not storing anything large in it and turning it off for all controls which do not need it   References for storing ViewState in SQL Server  MSDN - Overview of PageStatePersister ASP Alliance - Simple method to store viewstate in SQL Server Code Project - ViewState Provider Model

User · Answer

This is because of a huge view state  In my case I got lucky since I was not using the viewstate  I just added enableviewstate  false  on the form tag and view state went from 35k to 100 chars

User · Answer

My guess is that something is either encoding or decoding too often - or that you ve got text with multiple lines in   Base64 strings have to be a multiple of 4 characters in length - every 4 characters represents 3 bytes of input data  Somehow  the view state data being passed back by ASP NET is corrupted - the length isn t a multiple of 4   Do you log the user agent when this occurs  I wonder whether it s a badly-behaved browser somewhere    another possibility is that there s a proxy doing naughty things  Likewise try to log the content length of the request  so you can see whether it only happens for large requests

User · Answer

In addition to  jalchr s solution that helped me  I found that when calling ATL  Base64Encode from a c   application to encode the content you pass to an ASP NET webservice  you need something else  too  In addition to  sEncryptedString   sEncryptedString Replace               from  jalchr s solution  you also need to ensure that you do not use the ATL BASE64 FLAG NOPAD flag on ATL  Base64Encode    BOOL bEncoded   Base64Encode lpBuffer                      nBufferSizeInBytes                      strBase64Encoded GetBufferSetLength base64Length                        amp base64Length ATL BASE64 FLAG NOCRLF   ATL BASE64 FLAG NOPAD

User · Answer

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

[.net] What causing this "Invalid length for a Base-64 char array"

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