(WF4.5) Enabling new .Net framework 4.5 features in your rehosted designer application

[Minor disclaimer: content in this post is based upon a non-final release candidate build of .Net 4.5]

The workflow designer team had two slightly conflicting goals to tackle in .Net 4.5.

Goal one: Make Workflow Designer more awesome for everyone in .Net 4.5. It should be easier to use, it should look better, and it should let you do some cool new things that will just never work in 4.0.

Goal two: Be completely backwards compatible for applications build on .Net 4.0.

This second goal is a very important one because .Net 4.5 is an in-place upgrade. Basically, as soon as you have installed .Net 4.5 on your machine, there is no ‘separate’ .Net 4.0 on your machine. Every app that was built to use .Net 4.0 will automatically be loading .Net 4.5 assemblies once you make the upgrade. (And it doesn’t matter why you made the upgrade – you might have needed to upgrade in order to install new fancy application X from 3rd party developer Y, and suddenly your workflow designer app stops working – who will you call?)

So the designer team made a decision, and of the two goals, you’ll see the second goal landed on top. So while there are a lot of nice usability features in .Net 4.5 and none of them are turned on by default. They are all opt-in. And so you ask:

Opting in, by using DesignerConfigurationService

In order to opt in to 4.5 features, and likely future framework features (5.0??) we must take advantage of a new Service provided by the workflow designer’s EditingContext (at some point I might even get around to providing a 4.5 comparison version of services available as in this post - not today though – so feel free to beat me to that punch).  It’s called DesignerConfigurationService.

The first thing you want to do with DesignerConfigurationService is turn on all the good stuff!

Here’s a small code snippet enabling all of the little usability enhancements built into the 4.5 version of the rehostable workflow designer. A good time to call this would be before loading a root model item.

    DesignerConfigurationService configService =


    configService.AnnotationEnabled = true; /* maybe, see explanation of TargetFrameworkName*/

    configService.AutoConnectEnabled = true;

    configService.AutoSplitEnabled = true;

    configService.AutoSurroundWithSequenceEnabled = true;

    configService.BackgroundValidationEnabled = true;

    configService.MultipleItemsContextMenuEnabled = true;

    configService.MultipleItemsDragDropEnabled = true;

    configService.NamespaceConversionEnabled = true;

    configService.PanModeEnabled = true;

    configService.RubberBandSelectionEnabled = true;

The second and third things you probably want to do with DesignerConfigurationService is choose a XAML loading security setting, and identity the target framework that your workflow is intended to run on…

MAYBE like this (emphasis on maybe)

    configService.LoadingFromUntrustedSourceEnabled = false;

    configService.TargetFrameworkName = new FrameworkName(".NETFramework,Version=v4.5");

So what? What do these do?

Well, I haven’t any real source of info on LoadingFromUntrustedSoruceEnabled (the msdn docs are currently no help), but I am making a wild guess that it is something to do with whether you want to enable loading XAML files from ‘untrusted’ places like network shares. Sort of like the powershell set-executionpolicy setting.

Anyway I think the second setting is by far the more interesting of the two – it actually lets you be specific about what target framework you wish your workflow designer to be designing for. Now at the current date, you have only three realistic choices for this setting, and they are:

  1. new FrameworkName(".NETFramework,Version=v4.0");
  2. new FrameworkName(".NETFramework,Version=v4.0,Profile=Client");
  3. new FrameworkName(".NETFramework,Version=v4.5");

Selecting a target framework has various interesting effects, some of which you might not guess.

For instance setting v4.5…

  • is actually a secret requirement for setting Annotation.Enabled = true to work! (because annotation will save stuff in the XAML which only a 4.5 framework XAML loader will understand)
  • makes FlowDecision display names editable in the designer
  • in theory, enables custom language expression editors including C# expression editor - but you must provide the editor – C# editor is not built-in (sadly)

For instance setting v4.0…

  • enables a ‘best-effort’ load of XAML files which contain features found only in v4.5 framework so that later when you save the XAML you don’t accidentally save in any 4.5 features.

[Does setting a Client profile in the target framework actually do anything for a rehosted app? I don’t know!]

Comments (8)

  1. Ryan says:

    I just tried this out and it works great. Most of the properties are pretty self explanetory, but do you have any idea what NamespaceConversionEnabled does?

  2. John Hennesey says:

    "in theory, enables custom language expression editors including C# expression editor – but you must provide the editor – C# editor is not built-in (sadly)"

    Sorry for the novice question, but can you elaborate on this a little more?  I was under the impression I could flip a switch in 4.5 to allow c# syntax vs vb and it would work like magic.  Is this not the case?

  3. tilovell09 says:

    Hi Ryan,

    I asked some of the people who were involved in the feature development, and the quick information I got is that apparently NamespaceConversionEnabled changes the way the rehosted designer treats XAML files that were created with 4.0 framework. This is related to the change in namespace serialization formats in XAML files in 4.5 and 4.0. So it may, for instance, have some effects on whether files created in the designer using 4.5 features are runnable with only 4.0 framework installed.


  4. Ryan says:

    Thanks Tim!

  5. alecia says:

    I am using vs2010 RTM version and i have installed .net framework 4.5 but i am not able to use DesignerConfigurationService. I wanted to use the annotation functionality in WF4.5. please help.

  6. tilovell09 says:

    Hi Alecia,

    My experience so far with VS 2010 is that it won't allow me to target .Net 4.5 framework in my projects (I don't know if that will get fixed at some point later). For now I would suggest installing the VS 2012 release candidate in order to develop your rehosted app for .Net 4.5.


  7. alecia says:

    Yes i am not able to target .net4.5 in my vs2010 projects. But i read somewhere that if you install .net 4.5, it will overwrite version 4.0 and the name will still be 4.0? After installing .net 4.5, my project targets to 4.0 but there are some changes in the icons etc in the workflow so i guess it has the framework 4.5 features. Still i am not able to use the above code coz my project does not recognize 'DesignerConfigurationService'.

    I won't be able to change to any other versions of visual studio but 2010. Is there any way i can implement annotations with my current setup?

  8. tilovell09 says:

    >But i read somewhere that if you install .net 4.5, it will overwrite version 4.0 and the name will still be 4.0?

    That is correct, the framework's 4.0 dlls in your GAC will be replaced with 4.5 dlls. Having 4.5 installed doesn't stop you from *building* a project that targets 4.0, but since the replacement has happened you can only *run* it against 4.5 on that particular machine.

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