Debugging the Next Session in Business Central

Business Central v15 includes some good new stuff for developers. Access modifiers for objects, smarter code analysis, background page tasks – there is a list of stuff here: https://docs.microsoft.com/en-us/dynamics365-release-plan/2019wave2/dynamics365-business-central/developer-tools

I’ve just been trying out the new debugger capability, specifically being able to attach the debugger to a service and debug the next session to hit a breakpoint or error.

A Brief Nostalgia Trip…

Excuse me if I indulge in a little nostalgia. If you don’t care about this and just want to know how it works then you can skip to “spare me the history lesson”.

The Classic Client Years

Still here? Then maybe you have been around NAV long enough to remember the introduction of the RoleTailored Client. We’d been used to having the Classic Client debugger for years. It wasn’t perfect, but we knew our way round it. We could easily switch between writing and debugging code, debug an application server or even debug a posting routine in live and lock the whole system – anyone else do that when they first started in support? Life was good.

The RoleTailored Client Years

Then the RoleTailored Client was introduced and it felt like we were developing with one arm tied behind our backs. No debugger. You could still debug in Classic Client but the clients weren’t necessarily even running the same C/AL code – thanks to the ISSERVICETIER keyword.

I know you could find the source that the service tier was actually running, attach Visual Studio to the Server.exe process and debug the C# but not many people wanted to do that. MESSAGE debugging was far more common. Especially entertaining if someone left a message box in live and you got a call from the customer wondering what some mysterious pop-up was about. Connoisseurs wrapped their MESSAGEs in

IF USERID = 'sa' THEN...

By NAV 2013, RTC was the only client customers could use and we had to be able to debug. To be fair, Microsoft came up with the goods and the new debugger was better than what we used to have in the Classic Client. Especially because we could debug other sessions connected to the same service tier or the next session to connect. Ask the user to repeat the steps that lead to error and debug their session, perfect. Also great for debugging web service calls.

The Business Central Years

And then along came Business Central. The RoleTailored Client, complete with debugger is going to be removed and we don’t quite have a replacement for everything we rely on it for. Sound familiar?

Don’t get me wrong, I love VS Code. I love the VS Code debugging experience. But how can I debug other user sessions? How can I debug web service calls?

Spare me the History Lesson, How Does it Work?

Open up launch.json and hit the Add Configuration button in the bottom right hand corner and you’ll notice a couple of new options:

  • Attach to the next client on the cloud sandbox
  • Attach to the next client on your server

Pick one of those and you’ll notice that the configuration it creates has a request value of attach.

breakOnNext determines the type of session that the debugger will be attached to: Background, WebClient or WebServiceClient.

Give the configuration a sensible name so that you’ll be able to refer to it when you attach the debugger. Attach the debugger by opening the debug pane, selecting your configuration and click on the Start Debugging button.

Set some breakpoints in your code and hit them. Either with some activity in the web client or with a web service call.

BreakOnNext Support

Note: the help for breakOnNext states “The sandbox version only supports attaching to a WebService Client”. This seems to apply to sandbox Docker containers (e.g. from mcr.microsoft.com/businesscentral/sandbox) as well as to cloud sandboxes. You can, however, use the other breakOnNext options with an on-premise Docker image (mcr.microsoft.com/businesscentral/onprem).

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