Trick: Instantiating any control in a Control Add-in

My two last blog posts tackled two aspects of working with control add-ins: making any property or method accessible to C/AL, and making any event accessible to C/AL The first was a simple trick, the second was a bit more complex. Together, these two tricks enable you to easily interact with whatever Windows Forms control the add-in shows: you can access any of inner control’s members – properties, methods, or events. At this stage, there is a very simple, but robust framework in place, which lets you publish any kind of control and make it fully available to C/AL. Cool.

But, couldn’t we make it a bit cooler? How about being able to instantiate any control, and having C/AL decide which control to instantiate, instead of hardcoding it in the C# code?

Yes, we can do this.


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Trick: Subscribing to any Control Add-in event through pure C/AL

So, it worked. I found just enough spare time to try out the crazy idea I mentioned in the last post. It’s about control add-ins and events. In the last post I gave a tip about exposing the actual control as a property decorated with ApplicationVisible, which allowed you to directly access all properties and methods of the control.

However, if you wanted to do the same with the events, you had no other option but to manually create an event handler for each event type, then to add an event handler for the actual event from the original control, and finally to raise the event on your control add-in from the event handler for the actual control. You lost me already, so did I Smile

This is what I am talking about. Imagine a button, and that you want to allow NAV to respond to its Click event. This is what you need to do:


Might not seem too much, but consider that you must do this for every single event that you want to use, that it requires some rewrite-restart-redeploy-redesign-rebind workout to implement support for another event you forgot last time, and then it becomes an problem. Probably the ugliest part of it all is the fact that for C/SIDE to properly insert the new event triggers for an updated class, you have to unbind the Control Add-in, and then to re-bind it. This loses any C/AL code in previously existing triggers. Add to the equation the human error variable, which kind of readily pops up whenever manual code duplication is involved, and you’ll have a lot of happy hours fixing the mess and juggling dlls and C/AL code back and forth.

How about this. How about not having to add anything at all to your C# source code, and not having to redeploy anything, and then to support any event you want just through a single line of C/AL code?


Yes. That’s what this blog post is about.


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.NET Tips & Tricks: Mediator Pattern (on steroids)

When I was writing my last post I had a distinct feeling that I was trampling over some boundaries of good NAV design. After all, you should not do stuff like that, NAV isn’t meant to do things like that, or at least that was how I felt.

And then two things happened.

First, I asked myself: what the heck, why not? What exactly is NAV meant to do, and why not things like that? If folks at Vedbæk didn’t provide an out-of-the-box solution for the problem, why should the problem stay unsolved?

Second, my dear friend and a fellow MVP, Hrvoje of Hudo’s Vibe, identified the thing as the mediator pattern. So, the thing I’ve done to NAV, civilized world has been doing to their programming environments for a long time.

And then I decided to take it all to a different level altogether, and expand the simple class which didn’t do much but raise events on itself when its method was called, into a full-scale framework. And here it is, the mediator pattern incarnated into a brand new Dispatcher class, adapted to NAV, and with features that make it truly flexible. I do not dare starting to think what are all the situations where you could put this thing to use in NAV.

Read on.


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.NET Tips & Tricks: Dispatcher

There are situations when you want to exchange data between different objects in NAV, and there is no simple way to do it. One of those, that a friend stumbled upon a couple of days ago goes like this: you have a page which shows a subpage, that is linked to a factbox. Depending on the situation in the lines, you the factbox shows content from one table or another.

Your instincts may yell “ProviderID” at this moment, but there are some problems with it. ProviderID is used to set the link between different part controls on the same page. But if the link from the provider control results in no record being selected in the target part control, then the OnAfterGetRecord trigger in it does not fire, and you cannot update the content.

Another example may be this: depending on the line selected in the lines part, you may want to show either of two factboxes. Imagine – on a sales order, if you are on a line that sells a resource, you want to show the Resource factbox; and if you are on a line that sells an item, you want to show the Item factbox. You get the gist. There are not many ways you can achieve this.

As a matter of fact, when helping my colleague, I couldn’t think of any.

Except for an old trick which, unfortunately, does not work at all in the RTC. In the good old days of the Classic client, when heroes roamed the Earth, you could pass the CurrForm as a reference onto a function in a subform, which would then store the reference to the main form in its own Form variable. Then, when something happened in the lines, and you wanted to let the master page know, you called the function on the stored reference. It worked like charm. However, in NAV 2013 (and possibly 2009 – can’t bother to check) you cannot assign one page variable to another. Furthermore, the CurrPage variable has page ID in some funny range, and does not even correspond to the actual page number. All in all, no way you can pass, or retain, a reference to a page object, let alone the current page reference.

So, how do you have two, three, or more pages (or page parts, for that matter) talk to each other to pass some information when needed, in all those situations when ProviderID simply doesn’t get the job done (I could bore you to death listing those situations)?

.NET interoperability, what else.


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