My current working theory is that there are 2 separate (but possibly related) issues happening at the same time. One error when the user attempts to save the form (resulting in the loss of all their changes), and one when the browser attempts to reload/display it (resulting in the error message shown and the inability to go back to a view of the form with their updated content).

Here are some sanitised error messages I’ve captured from the event log when the problem happens.

InfoPath Forms Services has detected a mismatch between the user's data in the browser and on the server. This may indicate the SESSION_STATE_PASCAL_CASED is not configured properly on a multiple front end farm or that a malicious user is trying to tamper with client data. (User: DOMAIN\username, Form Name: Form, IP: , Request: http://website/_layouts/FormServer.aspx?XmlLocation=/filepath.xml&Source=http://website/Library/Forms/AllItems.aspx?RootFolder=%&FolderCTID=0x0120004AE5D17103937E4DAC784D461AF8C33D&View=%257b9AD631DA%252d5EDE%252d4EF1%252d8FF3%252d14ED56F1471A%257d&DefaultItemOpen=1, Form ID: urn:schemas-microsoft-com:office:infopath:Form:-myXSD-2009-09-01T01-30-36) 604f4e9e-bff3-460d-af19-229411e20ab9

WARNING: Invalid Canary for view file. StackTrace: at Microsoft.Office.InfoPath.Server.Controls.ResourcePage.GetSolutionAndVerifyCanary(HttpContext context, String solutionId, SPSite contextSite, ResourceErrorType& error) at Microsoft.Office.InfoPath.Server.Controls.ResourcePage.HandleViewFile(HttpContext context) at Microsoft.Office.InfoPath.Server.Controls.ResourcePage.<>c__DisplayClass2.b__0() at Microsoft.Office.Server.Diagnostics.FirstChanceHandler.ExceptionFilter(Boolean fRethrowException, TryBlock tryBlock, FilterBlock filter, CatchBlock catchBlock, FinallyBlock finallyBlock) at Microsoft.Office.InfoPath.Server.Controls.ResourcePage.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) at System.Web.HttpApplication.ApplicationStepManager.ResumeSteps(Exception error) at S

Don’t you love how that last stack trace just gets cut off like that? Woo!

Here is my current link log from researching the issue:

• Reading this now: http://blogs.msdn.com/b/shivajin/archive/2009/05/11/deep-dive-on-infopath-request-and-response.aspx
• This describes the error message I can’t reproduce. I’ve already verified that AAM isn’t the problem, the users are accessing the site via the Default Zone URL. http://social.msdn.microsoft.com/Forums/en-US/sharepointinfopath/thread/1729d3eb-b63f-462d-bbb6-53a735ad6b98/
• This could be more likely. All service accounts are domain accounts, but I do know that our client’s infrastructure had some odd AD policies that might be occasionally wreaking havoc somehow. http://blog.sharepointrx.com/2010/02/05/infopath-forms-server-error-there-has-been-an-error-while-loading-the-form-a-required-resource-could-not-be-downloaded-to-try-to-resume-the-download-refresh-the-page/
• This is also likely but I hope it’s not the case. Having people delete their temporary internet files is not going to really help the problem much if they’ve just lost an hour’s worth of work in their form. Even though this is ostensibly a workflow issue, the workflow forms are InfoPath, so it could be related. http://www.dev4side.com/community/blog/2010/6/11/error-there-has-been-an-error-while-loading-the-form-in-an-approval-workflow.aspx
• This one also suggests a caching/temporary files issue might be causing this. No, no! It can’t be true. Also, further reading indicates the suggestion to run stsadm -o reconvertallformtemplates is a really bad idea. http://vspug.com/ssa/2007/12/24/tip-session-state-pascal-cased-is-not-configured-properly/
• Once again suggesting IE’s caching is at fault: http://blog.jussipalo.com/2008/02/forms-server-invalid-canary-for-view.html
• More info on what the “Invalid canary” warning means: http://social.technet.microsoft.com/Forums/en/office2010/thread/0acbb4e3-4526-487d-8f67-781cc3bb63b1
• This post suggests SP2 will fix things… except the environment is already running SP2. Bother. http://blog.sharepointalist.com/2009/10/invalid-canary-for-view-file.html

My conclusion is that there is some type of caching, cookie expiry, session timeout bad juju going on. Unfortunately that’s not one I can document for an end user!


// C#
public DateTime GetStartOfWeek(DateTime date, DayOfWeek WeekStartDay) {
double daysToStart = (Convert.ToDouble(today.DayOfWeek) - Convert.ToDouble(WeekStartDay) + 7) % 7;
DateTime weekStartDate = date.AddDays(0 - daysToStart);
return weekStartDate;
}


Fortunately, Joel Oleson’s blog came to the rescue. The correct stsadm command to use to force this sucker to start is:

stsadm -o provisionservice -action start -servicetype SPWebService

It took a while for the command to complete, but that seemed to fix everything up nicely.

Deep Dive into the SharePoint Content Deployment and Migration API – Part 1

SharePoint 2007 – /_layouts and how to create pages that run in site context – Serge van den Oever

It is also a very useful link if you are doing any kind of custom development that requires a custom “settings” type page (for instance, if you are writing a custom workflow without InfoPath to handle the forms).

I also found that you may need to install a hotfix on your Windows 2003 VPC in order to install SP1 for Visual Studio in order to get the web application project type mentioned in that blog post. The hard way. After wasting many valuable hours.

• LINQ
  Extends the .NET framework for easy data query & transformation operations in a functional programming type approach. LINQ will be integrated into Visual Studio 2008, but you can use it now. I also found this very nifty LINQ to SharePoint provider on CodePlex that I will need to check out (could it be the end of having to manually compose CAML? Oh I hope so)!
• Dynamic Data Controls
  This ASP.NET library provides a set of web controls that bind to data sources and cut out a lot of the typical, repetitive drudgery of setting up a rich, data-driven web application with data listings, views, insert, update & delete operations & UI. And, even better, combine them with LINQ for some really simple, clean, maintainable code. We got a demo of the library that will be ready in the August ASP.NET futures download.
• WPF/XAML
  The Windows Presentation Foundation is a framework for developing rich applications using a declarative XML format (XAML) to control UI, and .NET managed code to handle the business logic/functionality. Having seen the demos, I think XAML is what XHTML should be! Well formed and with tons of functionality (like, *gasp* columns!). Better still, WPF applications will be able to work as web applications as well as Windows client applications.

Veerrry interesting… Is it especially geeky of me to contemplate chucking a sickie just so I can play around with new development technologies?

If you don’t know how SharePoint Features work, take a quick look at the SDK as it can explain it far better than I can. Essentially what feature stapling allows you to do is piggyback features into a specific existing site definition without actually altering that site definition. Since you can implement just about any type of SharePoint functionality as a feature, including creating lists, content types, content, changing site settings, adding UI elements, and so on, that means you can easily customise out of the box site definitions.

SHEESH! I wish I had payed more attention to this six months ago– it would have saved me so many headaches.

I did a quick search and found this very thorough blog post by Chris Johnson from November last year that covers how to do it. A big thank you to Ishai and Milan Gross for introducing this concept to me.