Issue Description
After upgrading from K2 4.6.11 to K2 4.7, the K2 Designer File Attachment Control intermittently causes the SmartForms Application Pool to stop. This happens when selecting a file and clicking OK in the file browse box.

Error Message
An unhandled Microsoft .NET Framework exception occurred in w3wp.exe [83836]

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APICommunicationException was unhandled --> An unhandled exception of type 'SourceCode.Hosting.Exceptions.APICommunicationException' occurred in SourceCode.Forms.dll. Additional Information: Not Connected

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Repro Steps

  1. Set ConnectionPooling to false in web.config for both Designer and Runtime.
  2. Add an attachment control onto a view.
  3. Save and publish the view.
  4. Run the view and load a file with the attachment control, refreshing and repeating until the error occurs.

Resolution

  1. Ensure you have K2 4.7 installed.
  2. Install the K2 4.7 February 2017 Cumulative Update.
  3. Get the K2 4.7 February 2017 Cumulative Update FP3 from Regional Support.
  4. Install the K2 4.7 February 2017 Cumulative Update FP3 to apply the fix.
  5. Clear the Browser Cache.