Managed Application Framework – Part 1 – The Beginnings!

Last week I was tasked with developing a new App for the guys I work with, (not a developers app you understand, but for actual normal users!!! Luckily it puts me smack bang where I work best – developing functional, extendable (and most importantly) Windows based apps. I’m now officially in my comfort zone!

The main difference between this app and previous apps I’ve done is the customer, normally I’m the person who writes that software tool that the other devs or system admins will use, so I can cram in shed loads of functionality and what I think are cool UI’s – usually involving liberal use of the SandDock tools (http://www.divelements.com/). This time because the users are non-expert users I’m having to really consider the design of the UI, and it is (in this case) very important – one of the specs of the app is: ‘It has to look cool’.

There is actually a reason for it to look cool – because we need it to impress management to get the go-ahead to redo an older app. Up side of this is that it’s going WPF. Aces!

Woah, I appear to have got a little bit sidelined.. I actually started this post to talk about the Managed Add-In Framework (MAF) of .Net 3.5. The MAF is a framework for using Add-In’s (or plugins as some apps call them) within .NET, but without the hassle of writing your own code to do the cool stuff (reflecting to load dlls etc).

As it happens MAF fits very nicely into the app I’m designing at the moment, so I’ve been playing around with it for a week or so now, and I have to say, I’m very impressed, the design of the MAF has been extremely well thought out, and covers a hell of a lot!

What does MAF consist of? Basically 3 broad parts, Host – Pipeline – Addin, of which the pipeline can be broken down into: HostView – HostAdapter – Contract – AddInAdapter – AddInView. The reason this is important is that the pipeline seperates the Host and AddIn from being dependent on the Contract (which in a later post will prove to be incredibly useful).

In this post (below) I’m going to explain how to set up a simple quick MAF application, just to get the swing of things, so.. without further ado: the MAF.

Firstly it’s important to know that the MAF requires a certain folder structure to work, (I think it requires it, every example, sample etc I’ve seen has it!). The structure can be seen on MSDN at: http://msdn2.microsoft.com/en-gb/library/bb384240.aspx – This is why I’ve put the fact that you need to set the output folders in the properties for projects created to point to a non-default location.

We begin creating a MAF project with a Class Library project we’re gonna call ‘Contracts’. In it we define the contract we intend to make all our Add-Ins implement.

  1. New Class Library – ‘Contracts’, set the Build Output to be: ..\Output\Contracts
  2. Add references to: System.AddIn and System.AddIn.Contract
  3. Define new interface, which must implement the IContract interface, and have the AddInContract attribute.


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

  1. Build the one project, all ok? Good, let’s mosey on!
  2. Get and install the Pipeline builder (open source) from codeplex: http://www.codeplex.com/clraddins
    (All the instructions are on the interweb at that site).
  3. Run the Pipeline builder and create the pipeline, this creates the 4 extra projects (HostView, AddInView, AddInSideAdapters and HostSideAdapters projects). This saves us the time of writing this code ourselves (which involves quite a lot of code repetition).
  4. Build the solution, you should have 5 projects now. Assuming that went ok, lets carry on.
  5. Create an Add-In —
    a) Add a new Class Library project to the solution, call it something like ‘AddInV1’
    b) Set the build output location to be: ..\Output\AddIns\V1
    c) Reference in the AddInView DLL which will be in the Output\AddInView directory.
    Set this reference’s ‘Copy to local’ property to ‘FALSE’.
    d) Reference in System.AddIn
    e) Edit the class file and create the code to implement the IHelloMAF contract:


[AddIn("AddInV1", Version="1.0.0.0")]
public class AddInV1 : IHelloMAF
{
public string HelloMAF() { return "Hello MAF!!"; }
}

In this code we’ve attached the ‘AddIn’ attribute, which takes a name (which can’t have spaces) and then a set of named properties (intellisense is your friend here). Also of note is that in our ‘Contracts’ project we called the contract: IHelloMAFContract, whereas here we’re using IHelloMAF. The code does nothing impressive, just returning a string.

  1. Build the solution, if you look in your output folder you should now have a \Addins\V1 directory with the dll in it. That’s the Add-In created.

  2. Now we’re going to create a host to actually run the Addins
    a) Create a new Console Application (call it something memorable, ‘host’ for example :))
    b) Reference the HostView dll (copy to local = false) and the System.AddIn dll.
    c) Set the build output location to: ..\Output
    d) In the Program.cs file, put in the following:


public static void Main()
{
string path = Environment.CurrentDirectory;
//Update the AddInStore looking for the AddIns.
AddInStore.Update(path);

//Get the tokens from the AddInStore.
Collection tokens = AddInStore.FindAddIns(typeof(IHelloMAF), path);

Console.WriteLine("Found " + tokens.Count + " addins, activating them....");

foreach(AddInToken token in tokens)
{
//Activate a given token.
IHelloMAF addin = token.Activate( AddInSecurityLevel.Internet );
Console.Write( "\tAddin: " + token.Name + ", version: " + token.Version + " --> " );
Console.WriteLine( addin.HelloMAF() );
}

Console.WriteLine();
Console.WriteLine( "Fin. Press ENTER to exit." );
Console.ReadLine();
}

What we have here are 3 main points, firstly where we do: AddInStore.Update(path); We’re telling the AddInStore to update itself and look for AddIns with the given root path.

Next point is the AddInStore.FindAddIns(typeof(IHelloMAF), path); line, which basically asks the AddInStore to find the AddIns available of a given type.

The final point is the activation of the AddInToken – token.Activate( AddInSecurityLevel.Internet );. At this point we’re activating the Add-In, and in the next lines calling methods on it.

  1. Build the solution.
  2. Start debugging (F5).

Running this should now give us:

> Found 1 addins, activating them....
> Addin: AddInV1, version: 1.0.0.0 --> Hello MAF!!
> Fin. Press ENTER to exit.

That’s the basic Host Pipeline AddIn structure, and will provide you with a good basis, the next step is to consider what to do in the event that we want to change the contract…