What does a stacktrace mean when there are two of them? - asp.net

Question

I have an MVC application and it has essentially two stacktraces, im wondering why there are two of them though?..
[MissingMethodException: No parameterless constructor defined for this object.]
System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98
System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241
System.Activator.CreateInstance(Type type, Boolean nonPublic) +69
System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +67
[InvalidOperationException: An error occurred when trying to create a controller of type 'PteDotNet.Web.Controllers.BlogController'. Make sure that the controller has a parameterless public constructor.]
System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +182
System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80
System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +74
System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +232
System.Web.Mvc.<>c__DisplayClass6.<BeginProcessRequest>b__2() +49
System.Web.Mvc.<>c__DisplayClassb`1.<ProcessInApplicationTrust>b__a() +13
System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7
System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22
System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Func`1 func) +124
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +98
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +50
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8970356
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184

Answer 1

One is a stacktrace of an inner exception.
It looks like you first got a MissingMethodException, with reason
No parameterless constructor defined for this object.
That caused an InvalidOperationException, with reason
An error occurred when trying to create a controller of type 'PteDotNet.Web.Controllers.BlogController'. Make sure that the controller has a parameterless public constructor.
So apparently your BlogController needs a parameterless constructor.

Answer 2

I'am not completely sure, but It looks like the Root Cause:
The MissingMethodException is fired first, then the InvalidOperationException gets fired, because of the first Exceptin

Answer 3

The InvalidOperationException is the exception thrown, but it is thrown as a result of a MissingMethodException and this exception is included as the InnerException of the InvalidOperationException. The InvalidOperationException explains what went wrong but looking at the InnerException you can see where the failure was triggered in the first place.
When you evaluate ToString() on an exception with an inner exception you get stack traces of all nested inner exceptions to help you understand the problem. A common mistake is to use ex.Message + ex.StackTrace for diagnostics purposes but you loose information about inner exceptions. Unless you want to hide this valuable information you should always use ex.ToString() when logging exceptions.
In the MVC framework there is code similar to this:
try {
// Will throw MissingMethodException if there is no parameterless constructor.
var controller = Activator.CreateInstance(type);
...
}
catch (MissingMethodException ex) {
var message = String.Format("An error occurred when trying to create a controller of type '{0}'. Make sure that the controller has a parameterless public constructor.", type);
throw new InvalidOperationException(message, ex);
}
So instead of getting a MissingMethodException which might confuse you, you get an InvalidOperationException with a nice explanation. This is an example of best practice when it comes to exception handling.