Skip to main content

Managing Change in Long Running Workflows Part 1


I’ve been using Workflow Foundation now for over a year and it has become an integral part of our architecture and has by and large been very successful. However it is not without it’s issues, the single most being that official documentation is light at best and relevant blog posts are quite rare.  

I recently ran into a fairly serious problem after deploying a new release of our Software.

The Problem

I received this lovely email from our exception tracker:

System.Runtime.DurableInstancing.InstancePersistenceCommandException: The execution of the InstancePersistenceCommand named {urn:schemas-microsoft-com:System.Activities.Persistence/command}LoadWorkflow was interrupted by an error. ---> System.Runtime.Serialization.SerializationException: Deserialized object with reference id '73' not found in stream.

The key part is “Deserialized object with reference id '73' not found in stream.” As I’m sure you can tell this does not really provide any helpful information.

The stack trace does give you some more information as to which property failed, but depending on the object graph the stack trace can be fairly massive.

This is the part which gives you the biggest clue:

at ReadArrayOfPersonFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )

The Cause

Basically what has happened here is that when trying to load an unloaded workflow instance from the SqlWorkflowInstanceStore the deserializer spits the dummy because a property on the object that existed at the time the Workflow was persisted no longer exists on the class. 

Once you understand the cause it does seem reasonable, sort of. In my effort to clean up the solution and get rid of unused properties I had effectively broken every workflow instance which was persisted before the date of the latest release.

As it turns out it’s possible to create this issue by either removing properties or renaming existing properties.

I made the fatal mistake of using passing my Domain Entities into the workflow as an argument.

The Patch

In order to fix this issue I ended up scrambling through the check-in history over the last 6 weeks trying to figure which properties had been removed. Once I figured it out, I added them back and deployed a patch. This solved the problem and the crisis was averted for the short-term.

The Solution

When a workflow is unloaded and persisted to the data store it is serialized and all internal variables & arguments are serialized along with it.

Rules for data objects in workflows:

  • Never ever under any circumstances use Domain Entities
  • Always use DTO’s for Arguments or Variables in Long Running Workflows
  • Set IsRequired=false on the DataMember attribute for all Nullable Properties
  • Set the Name property on the DataMember attribute
  • Set the Order Property on the DataMember attribute
  • Set the Name on the DataContract attribute


This is an example of a class that could create problems in the future.

    public class Category
        public int Id { get; set; }

        public List<Product> Products { get; set; }

Based on the above lessons here is how I would suggest coding this class for use in a Workflow.

   public class Category
       [DataMember(IsRequired = false, Name = "Id", Order=0)]
       public int Id { get; set; }

       [DataMember(IsRequired = false, Name = "Products")]
       public List<Product> Products { get; set; }

By setting the Name property on the DataMember you are then free to change the property name without fear of breaking the deserialization.

Setting IsRequired to False allows you to remove the property in the future without breaking deserialization, obviously you should set this for True for any properties that are truly required by the Workflow to function correctly.


This is just an example of how to deal with data that changes in workflows, in my next post I’m going to cover how you deal with workflows whose logic changes after an instance has been created and persisted.

I hope this helps anyone who’s working with Workflow Foundation or about to start using it.

Till next time.

Popular posts from this blog

Freeing Disk Space on C:\ Windows Server 2008

  I just spent the last little while trying to clear space on our servers in order to install .NET 4.5 . Decided to post so my future self can find the information when I next have to do this. I performed all the usual tasks: Deleting any files/folders from C:\windows\temp and C:\Users\%UserName%\AppData\Local\Temp Delete all EventViewer logs Save to another Disk if you want to keep them Remove any unused programs, e.g. Firefox Remove anything in C:\inetpub\logs Remove any file/folders C:\Windows\System32\LogFiles Remove any file/folders from C:\Users\%UserName%\Downloads Remove any file/folders able to be removed from C:\Users\%UserName%\Desktop Remove any file/folders able to be removed from C:\Users\%UserName%\My Documents Stop Windows Update service and remove all files/folders from C:\Windows\SoftwareDistribution Deleting an Event Logs Run COMPCLN.exe Move the Virtual Memory file to another disk However this wasn’t enough & I found the most space was

3 Reasons Why Progressive Web Apps (PWAs) Won’t Replace Native Apps

Many people believe Progressive Web Apps (PWAs) are the future of the mobile web, but in my opinion, PWAs are not a replacement for native mobile apps. Here are three reasons why: 1. Native mobile apps provide a smoother & faster experience  Mobile websites, progressive or otherwise are slower and not as smooth. 90% of the time spent is spent using apps vs the browser . The single most significant contributing factor to a smooth experience on mobile is the speed of the network and latency of the data downloaded and uploaded. When you visit websites on desktop or mobile, there is a lot of third-party code/data that gets downloaded to your device, which more often than not has zero impact on the user experience. This includes: CSS (Cascading Style Sheets) JavaScript Ad network code Facebook tracking code Google tracking code The median number of requests a mobile website makes is a shocking  69 . On the other hand, native apps only get the data that is requi

Unit Testing Workflow Activities in .NET 4.0

  Recently during a catch up with my buddy Keith Patton I was (as I tend to do) singing the praises of the Workflow in .NET 4.0. The all important question about Unit Testing support was raised, I tried as best as I could to explain the new In and Out Arguments but I didn’t feel I was convincing enough, so I though I would clarify with a blog post. If you developed Workflows in .NET 3.5 then you will be well aware of the lack of Unit Test support which was due to many reasons but mostly in part to the complex Workflow hosting environment. When moving to .NET 4.0 Workflow Foundation from .NET 3.5 it pays to be conscious of that fact that there is no longer a distinction between Activities and Workflows. Everything derives from the System.Activities.Activity class. So the definition of a Workflow is just a collection of of 1 or more Activities. I have designed a very simple Rental Car Activity which takes the an Applicants age as the input and outputs a True or False depending o