By now you should be able to get your Azure Function triggered from Dynamics 365 and connect back to Dynamics 365 to do some evil awesome things. Debugging Azure Functions however, is not a walk in a park – not like you can set breakpoints and step through the code.

Well, you should, of course, write some nice classes doing the job, test them using test harness or, at very least, a simple console application and then refer to those classes in your Azure Function code.

If something goes wrong in production and you need to get to the bottom of it, all Azure Functions entry points provide TraceWriter that you can use to dump the information required. That’s in your code but what about mysterious internals of Xrm Tooling black box? What if your code cannot connect to Dynamics 365 instance?

TraceWriter is an abstract class implemented in Azure WebJobs SDK while Xrm Tooling utilizes System.Diagnostics Debug/Trace/TraceListener model.

Create additional file ToolingListener.csx

using System;
using System.Diagnostics;

// Log writter for working with Azure Functions 
// for the Xrm.Tooling.Connector
public class Toolinglistener : TraceListener
{
  private TraceWriter _log;

  public Toolinglistener(string name, 
            TraceWriter logger) : base(name)
  {
    _log = logger;
  }

  public override void Write(string message)
  {
    _log?.Info(message);
  }

  public override void WriteLine(
            string message)
  {
    _log?.Info(message);
  }
}

Then add the following to the original function:

#load "ToolingListener.csx"

using System;
using System.Diagnostics;
using Microsoft.Xrm.Tooling.Connector;

public static void Run(string input, TraceWriter log)
{
    TraceControlSettings.TraceLevel = SourceLevels.All;
    TraceControlSettings.AddTraceListener(
		new ToolingListener(
			"Microsoft.Xrm.Tooling.CrmConnectControl", 
			log));

And you should see very detailed output in your function log:

Of course, the code takes a shortcut with log.Info and requires a bit of tuning like mapping logging levels from Connector to TraceWriter but those are the details we can live without, right?