Managed Application Framework – Part 2 – Basic Versioning!

Soooo… A post from a while ago covered the basic Managed Addin Framework (MAF from here-in) and how to set up a basic addin with host and pipeline.

One of the big problems of an Addin situation is if we change the contract between our Addins and our host. This can happen for a number of reasons – added functionality, removed functionality, the dreaded security etc… So, we change our contract and OH NOES! break all the AddIns we’ve carefully nurtured to maturity.

Luckily the guys who developed the MAF have come up with a solution to this, and it all lies with the pipeline………

Previously we had the IHelloMAF contract:

[AddInContract]
public interface IHelloMAF : IContract
{
string HelloMAF();
}

Obviously this gives us a limited set of functionality, so lets add a little bit more:

[AddInContract]
public interface IHelloMAF : IContract
{
string Hello(string name);
}

This will give us the power to accept inputs! Of course, this is just the contract, the detail is in the actual implementation itself.

If I simply update the contract and rebuild the pipeline, then my previously created AddIn will stuff up as it implements the old contract, I would have to change the AddIn to implement the new version, but I don’t or maybe can’t do that.

What does that mean for the development? Basically, we need to create another adapter, one to convert version 1 addins to work as a version 2 addin. To do this, we use the Pipeline builder, it saves a lot of time and effort in the long run. We need to be able to tell the Pipeline builder that, actually, generate a new AddInView, not overwrite the existing one. To do this, we reference in the PipelineHints dll (this is in the location you installed the PipeLine builder – in my case: C:\Program Files\Microsoft\Visual Studio Pipeline Builder\PipelineHints.dll).

Once we have the hints dll referenced we can go to our Contract file and put the following in:

[assembly: PipelineHints.SegmentAssemblyName(PipelineHints.PipelineSegment.AddInView, “AddInView2”)]

** Put this ABOVE the namespace declaration (if you have one)!! **

What this effectively does is force the Pipeline builder to create the AddInView segment for this contract, but name it ‘AddInView2’ rather than it’s default ‘AddInView’.

If we now run the Pipeline builder, we will generate some new projects, including ‘AddInView2’, note – the ‘AddInView’ project is still there, aces!

After this we need to update the host to cope with the new contract (** IF we changed the contract name, if we didn’t then no updates required **), should be pretty simple.

We can then create a new AddIn, based off of the new contract, and once we’ve done that, run the host and load up our new AddIn. All should be working!

But the version 1 addin isn’t showing – this is expected at the moment. The pipeline builder has only created a pipeline for the new style of Addin. What we need to develop is a v1 addin to v2 addin adapter. The easiest thing to do is copy from the AddInSideAdapters project.

We create a new Class Library project, calling it something like AddInV1ToV2Adapter, which gives us a good start point.
Add in references to:
System.AddIn
System.AddIn.Contract
AddInView (the version 1 addin!)
Contracts
(Again, Copy to local = FALSE!!)

Then opening the AddInSideAdapters project, copy the IXXXViewToContractAddIn.cs contents and paste them into your ‘Class1.cs’ file. Now we just need to edit the code to do our translation, so.. first things first, rename the class, doesn’t really matter what it’s called!

You should find the only thing you really need to change is the implementation of the methods, so in our example, we’d have:

public virtual string Hello(string msg)
{
return _view.HelloWorld();
}

Rebuild the entire solution and run the host… Now our host detects 2 AddIns, which is perfect!

I would attach the code to this post, but my blog host doesn’t allow attachments at the moment, I am in the process of looking into this!
If you want it, please email me: cs7kardon [-=At=-] xc7lave . c7o . uk (remove the ‘7’s and compress!)

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