Thursday, March 28, 2019

How to log EWS Traces to a file in PowerShell

If your using the EWS Managed API in your PowerShell scripts and you need to do some extended debugging to work out why a script isn't working the way you expect in certain environments you can do this by using Tracing as described in https://docs.microsoft.com/en-us/previous-versions/office/developer/exchange-server-2010/dd633676(v=exchg.80) . What this does once it is enabled is it outputs all the requests and responses that are sent to and from the Exchange server so you can see exactly what is taking place and potentially more information on particular errors that are occurring.  So in a EWS Managed API script to enable this you just need to set the TraceEnabled property on the ExchangeService object to true eg

$server.TraceEnabled = $true

And you will then start seeing traces like the following in the console



A much cleaner way of capturing these traces is to configure the EWS Managed API to use a separate log file to log them to a file so you can review them later. To do this it requires that you create a class that implements an Interface of ITraceListener https://github.com/OfficeDev/ews-managed-api/blob/70bde052e5f84b6fee3a678d2db5335dc2d72fc3/Interfaces/ITraceListener.cs .  In C# this a pretty trivial thing to do but in PowerShell its a little more complicated. However using Add-Type in PowerShell gives you the ability to simply define your own custom class that implements the interface and then compile this on the go which then makes it available in your PS Session. The basic steps are

  • You need to define an class that implements the interface (through inheritance) and the methods defined in that interface in this case it only has one called Trace
  • Define your own code to perform the underlying logging in my example its a simple one liner that will append the Tracemessage to a File the path of which is held in the Public Property I've defined in my class 
  • Use Add-Type to compile the class and make it available in your PS Session
  • Create a Instance of the Class you just defined eg here's a function to do it
eg
function TraceHandler(){
$sourceCode = @"
    public class ewsTraceListener : Microsoft.Exchange.WebServices.Data.ITraceListener
    {
        public System.String LogFile {get;set;}
        public void Trace(System.String traceType, System.String traceMessage)
        {
            System.IO.File.AppendAllText(this.LogFile, traceMessage);
        }
    }
"@    

    Add-Type -TypeDefinition $sourceCode -Language CSharp -ReferencedAssemblies $Script:EWSDLL
    $TraceListener = New-Object ewsTraceListener
   return $TraceListener


}

Then in your PS Code just use the Instance (Object) of the Class you just created (first setting the LogFile property to path of the File you want to log to) eg

        $service.TraceEnabled = $true
        $TraceHandlerObj = TraceHandler
        $TraceHandlerObj .LogFile = "c:\Tracing\$MailboxName.log"
        $service.TraceListener = $TraceHandlerObj