Centralizing VSTO add in exception management with postsharp 6
After much reading around trying to find the best way to implement a global exception handler for a VSTO add-in on social msdn, stackoverflow and the Add-in Express forum I came across this solution using postsharp, this was the best solution I found but was 11 years old and relevant to postsharp 2, the library has changed a lot since then and the PostSharp.Laos namespace no longer exists as explained the postsharp support forum. ## The Solution in PostSharp 6
Happily this is still possible with PostSharp Community and is well documented in the postsharp handling exceptions documentation. First create a class which inherits from OnExceptionAspect for example VstoUnhandledExceptionAttribute. csharp using Microsoft.Extensions.Logging; using PostSharp.Aspects; using PostSharp.Serialization; namespace MarkZither.KimaiDotNet.ExcelAddin \\\{ [PSerializable] public class VstoUnhandledExceptionAttribute : OnExceptionAspect \{ public override void OnException(MethodExecutionArgs args) { ExcelAddin.Globals.ThisAddIn.Logger.LogCritical(args.Exception, "Handled by postsharp OnExceptionAspect"); args.FlowBehavior = FlowBehavior.Return; \\} } } This step will vary depending on how you are doing logging in your VSTO Add-In, I chose to use Microsoft.Extensions.Logging, while it arrived with .NET Core it is a .NETStandard 2.0 library and compatible all the way back to .NETFramework 4.6.1. csharp private void ThisAddIn_Startup(object sender, System.EventArgs e) \\{ instantiate and configure logging. Using serilog here, to log to console and a text-file. var loggerFactory = new Microsoft.Extensions.Logging.LoggerFactory(); var loggerConfig = new LoggerConfiguration() .MinimumLevel.Debug() .WriteTo.File("c:\\temp\\logs\\myapp.txt", rollingInterval: RollingInterval.Day) .CreateLogger(); loggerFactory.AddSerilog(loggerConfig); // create logger and put it to work. var logProvider = loggerFactory.CreateLogger<ThisAddIn />(); logProvider.LogDebug("debiggung"); Logger = logProvider; Configure PostSharp Logging to use Serilog LoggingServices.DefaultBackend = new MicrosoftLoggingBackend(loggerFactory); Globals.ThisAddIn.ApiUrl = Settings.Default?.ApiUrl; Globals.ThisAddIn.ApiUsername = Settings.Default?.ApiUsername; this.Application.WorkbookActivate += Application_WorkbookActivate; this.Application.WorkbookOpen += Application_WorkbookOpen; \} There is one important line in the logging setup which differs to the PostSharp Logging documentation at the time of writing, LoggingServices.DefaultBackend = new MicrosoftLoggingBackend(loggerFactory); which needs using PostSharp.Patterns.Diagnostics.Backends.Microsoft;. This is also useful for trace logging which I will explain further in the next section. Now decorate methods or entire classes with the [VstoUnhandledException] attribute and every exception will be handled by the OnException method. ## Bonus functionality in PostSharp community
As I had logging working I also made use of the features of PostSharp Logging