Couldn't find type for class Microsoft.WindowsAzure.Diagnostics

Question

Just got back from holidays, and went in to make a couple small changes in our app, when I was confronted by this error:

Couldn't find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35.

The code had been running perfectly prior to coming back from holidays. It was last published to Azure 3 weeks ago, and it is now having the same issue there. Locally I attempted to fix it by removing add adding the following config section back:

<system.diagnostics>
    <trace>
        <listeners>
            <add type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="AzureDiagnostics">
            </add>
        </listeners>
    </trace>
</system.diagnostics>

Add adding and removing the Reference to the assembly:

When I debug the project locally, Visual Studio breaks on the following line:

NewRelic.Api.Agent.NewRelic.IgnoreTransaction();

This had been working both locally and in production until 2 days ago (according to the error log).

Full Stack Trace:

[ConfigurationErrorsException: Couldn't find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35.]
   System.Diagnostics.TraceUtils.GetRuntimeObject(String className, Type baseType, String initializeData) +6755367
   System.Diagnostics.TypedElement.BaseGetRuntimeObject() +45
   System.Diagnostics.ListenerElement.GetRuntimeObject() +83
   System.Diagnostics.ListenerElementsCollection.GetRuntimeObject() +143
   System.Diagnostics.TraceInternal.get_Listeners() +181
   System.Diagnostics.TraceInternal.WriteLine(String message) +119
   System.Diagnostics.Trace.WriteLine(String message) +4
   NewRelic.Api.Agent.NewRelic.IgnoreTransaction() +13
   Linklicious2.Controllers.ApiController.GetLinksToPing(Boolean test) +46
   lambda_method(Closure , ControllerBase , Object[] ) +98
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +14
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +214
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27
   System.Web.Mvc.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12() +55
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +253
   System.Web.Mvc.<>c__DisplayClass17.<InvokeActionMethodWithFilters>b__14() +21
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +191
   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +324
   System.Web.Mvc.Controller.ExecuteCore() +106
   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +91
   System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10
   System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +34
   System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +19
   System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +10
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
   System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +48
   System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7
   System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9631764
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

If you aren't running in the emulator, then see my SO answer here - How to solve Windows Azure Diagnostic Runtime Error (Could not create WindowsAzure.Diagnostics, Version=xx, Culture=neutral, PublicKeyToken=xx. Basically, just add:

<filter level="TraceEventType.Error" />

in the <listeners><add> section.