The automapper error collection was changed when multiple users create a user

Question

I get the following error, and this error only occurs when several users click the same button. Any help / ideas would be really appreciated:

System.InvalidOperationException: The collection has been modified; enumeration operation cannot be performed. Generated: Wed, 10 Jun 2015 07:29:06 GMT

AutoMapper.AutoMapperMappingException:

Mapping types: User → User ApplicationSecurityManager.Service.User → ApplicationSecurityManager.Models.User

Target Route: User

Initial value: ApplicationSecurityManager.Service.User ---> System.InvalidOperationException: the collection has been changed; enumeration operation cannot be performed. in System.Collections.Generic.List 1.Enumerator.MoveNextRare() at AutoMapper.TypeMap.<get_AfterMap>b__1(Object src, Object dest) at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.Map(ResolutionContext context, IMappingEngineRunner mapper) at AutoMapper.Mappers.TypeMapMapper.Map(ResolutionContext context, IMappingEngineRunner mapper) at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) --- End of inner exception stack trace --- at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) at AutoMapper.MappingEngine.Map[TDestination](Object source, Action 1 choice) in ApplicationSecurityManager.UserManager.LoadUser (username String) in ApplicationSecurityManager.UserManager.get_AuthenticatedUser () in ApplicationSecurityManager.UsAeManager.sermanager. Infrastructure.ApplicationSecurityAttribute.OnAuthorization (AuthorizationContext fil terContext) in System.Web.Mvc.ControllerActionInvoker.InvokeAuthorizationFilters (ControllerContext controllerContext, IList 1 filters, ActionDescriptor actionDescriptor) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult 1.Begin (AsyncCallback callback, object state, Int32 timeout) when System.Web.Mvc.Async.AsyncResultWrapper.Begin [TResult] (AsyncCallback callback, object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate 1 endDelegate, Object tag, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate . Mvc.Controller <. > C__DisplayClass1d.b__17 (AsyncCallback asyncCallback, Object asyncState) with System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate 1 endDelegate, object tag, Int32 timeout) in System.Web.Mvc.Controller.BeginExecuteCore 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate ) with System.Web.MvcultAs. WrappedAsyncResult 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate tag 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate 1 endgevateDelegate 1 endgevateDelegate System.Web.Mvc.Async.AsyncResultWrapper.Begin (AsyncCallback callback, Object state, Be ginInvokeDelegate beginDelegate, EndInvokeDelegate endDelegate, Object tag) in System.Web.Mvc.Controller.BeginExecute (RequestContext requestContext, AsyncCallback callback, object state) in System.Web.Mvc.MvcHandler <. > C__DisplayClass8.b__2 (AsyncCallback asyncCallback, Object asyncState) when System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate 1 endDelegate, object tag, Int32 timeout) in System.Web.Mvc.Async.AsyncResultWrapper.Begin 1.Begin(AsyncCallback callback, Object state, Int32 timeout) at System.Web.Mvc.Async.AsyncResultWrapper.Begin[TResult](AsyncCallback callback, Object state, BeginInvokeDelegate beginDelegate, EndInvokeDelegate in System.Web.Mvc.MvcHandler.BeginProcessRequest (HttpContextBase httpContext, AsyncCallback callback, object state) in System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute () step IExecutionStep, Boolean & completedSynchronously)

This is the constructor where I think that the problem after installation is the problem, but when debugging I do not get an error.

 Public Sub New(environmentCode As String, applicationCode As String) MyBase.New(environmentCode, applicationCode) SOBaseUrl = System.Configuration.ConfigurationManager.AppSettings(Enums.AppSettingKeys.SOBaseUrl.ToString()) If Not String.IsNullOrEmpty(SOBaseUrl) Then SOBaseUrl = SOBaseUrl.TrimEnd("/") End If 'Setup mapping. Mapper.CreateMap(Of Service.User, Models.User)() _ .ForMember(Function(dest As Models.User) dest.ENumber, Sub(opt) opt.MapFrom(Function(src As Service.User) src.INumber)) _ .AfterMap(Sub(src As Service.User, dest As Models.User) dest.Groups = New List(Of String) Using service = ApplicationSecurityManager.Service.Factory.GetService() Dim applicationPermissions = service.LoadPermissionsForUser(dest.Username, MyBase.EnvironmentCode) If (Not applicationPermissions Is Nothing AndAlso applicationPermissions.Any(Function(x) x.Code = MyBase.ApplicationCode)) Then dest.Groups = applicationPermissions.Single(Function(x) x.Code = MyBase.ApplicationCode).GroupNames.ToList() End If End Using End Sub) 

Display attachments:

 container.RegisterType(Of IUserManager, UserManager)(New PerThreadLifetimeManager(), New InjectionConstructor( ConfigurationManager.AppSettings(Common.Enums.AppSettingKeys.Environment.ToString()), ConfigurationManager.AppSettings(Common.Enums.AppSettingKeys.ApplicationCode.ToString())) ) 

An saveUserResponse occurs in saveUserResponse .

  Public Function Create(user As Common.Models.User, approve As Boolean) As SO.Common.Models.User Implements IUserProvider.Save Dim saveUserResponse = UserManager.SaveUser(Mapper.Map(Of ApplicationSecurityManager.Service.User)(user)) If Not String.IsNullOrEmpty(saveUserResponse.ErrorMessage) Then 'The Security system returned an error. Throw New Exception("Security Service returned error: " & saveUserResponse.ErrorMessage) End If 'Return the username. Return Mapper.Map(Of Common.Models.User)(saveUserResponse.User) End Function 

Answer 1

This is because multiple users modify the same user.Groups directory in the AfterMap () method of your mapping. To avoid this, block the code that processes the collection. For instance:

 'class level object private object _myLock = New object() 'Setup mapping. Mapper.CreateMap(Of Service.User, Models.User)() _ .ForMember(Function(dest As Models.User) dest.ENumber, Sub(opt) opt.MapFrom(Function(src As Service.User) src.INumber)) _ .AfterMap(Sub(src As Service.User, dest As Models.User) SyncLock _myLock dest.Groups = New List(Of String) Using service = ApplicationSecurityManager.Service.Factory.GetService() Dim applicationPermissions = service.LoadPermissionsForUser(dest.Username, MyBase.EnvironmentCode) If (Not applicationPermissions Is Nothing AndAlso applicationPermissions.Any(Function(x) x.Code = MyBase.ApplicationCode)) Then dest.Groups = applicationPermissions.Single(Function(x) x.Code = MyBase.ApplicationCode).GroupNames.ToList() End If End Using End SyncLock End Sub) 

Answer 2

This is a fairly common mistake modifying a collection when iterating over it. Is it possible that you leave something here, we cannot see? In any case, the code you provided does not have such a scenario from what I see. This means that you can invoke this in a multi-threaded environment, and the collection will be modified in another thread.

What you can try?

Look at the lock on your enumeration to access one thread at a time. It is possible that it is accessed several times when the user clicks a button.

Here is a good link to help you: http://weblogs.asp.net/leftslipper/mvc-locking-the-routecollection