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PONHibernate: Collection was modified; enumeration operation may not execute
 

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    <p>I'm currently struggling with this "<strong>Collection was modified; enumeration operation may not execute</strong>" issue. </p> <p>I have searched about this error message, and it's all related to the foreach statement. I do have the some foreach statements, but they are just simply representing the data. I did not using any <strong>remove</strong> or <strong>add</strong> inside the foreach statement.</p> <p>NOTE: </p> <ol> <li>The error randomly happens (about 4-5 times a day).</li> <li>The application is the MVC website.</li> <li>There are about 5 users operate this applications (about 150 orders a day). Could it be some another users modified the collection, and then occur this error?</li> <li>I have log4net setup and the settings can be found <a href="http://community.jboss.org/wiki/Configuringlog4netforusewithNHibernate" rel="noreferrer">here</a> </li> <li><em>Make sure that the controller has a parameterless public constructor</em> I do have parameterless public constructor in AdminProductController</li> </ol> <p>Does anyone know why this happen and how to resolve this issue?</p> <p>A friend (Oskar) mentioned that </p> <blockquote> <p>"Theory: Maybe the problem is that your configuration and session factory is initialized on the first request after application restart. If a second request comes in before the first request is finished, maybe it will also try to initialize and then triggering this problem somehow."</p> </blockquote> <p>Many thanks.</p> <p>Daoming</p> <p><strong>Here is the error message:</strong></p> <p><strong>System.InvalidOperationException Collection was modified; enumeration operation may not execute. System.InvalidOperationException: An error occurred when trying to create a controller of type 'WebController.Controllers.Admin.AdminProductController'. Make sure that the controller has a parameterless public constructor. ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> NHibernate.MappingException: Could not configure datastore from input stream DomainModel.Entities.Mappings.OrderProductVariant.hbm.xml ---> System.InvalidOperationException: Collection was modified; enumeration operation may not execute.</strong> at System.Collections.ArrayList.ArrayListEnumeratorSimple.MoveNext() at System.Xml.Schema.XmlSchemaSet.AddSchemaToSet(XmlSchema schema) at System.Xml.Schema.XmlSchemaSet.Add(String targetNamespace, XmlSchema schema) at System.Xml.Schema.XmlSchemaSet.Add(XmlSchema schema) at NHibernate.Cfg.Configuration.LoadMappingDocument(XmlReader hbmReader, String name) at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name) --- End of inner exception stack trace --- at NHibernate.Cfg.Configuration.LogAndThrow(Exception exception) at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name) at NHibernate.Cfg.Configuration.AddResource(String path, Assembly assembly) at NHibernate.Cfg.Configuration.AddAssembly(Assembly assembly) at DomainModel.RepositoryBase..ctor() at WebController.Controllers._baseController..ctor() at WebController.Controllers.Admin.AdminProductController..ctor() at System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) --- End of inner exception stack trace --- at System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) at System.Activator.CreateInstance(Type type, Boolean nonPublic) at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) --- End of inner exception stack trace --- at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) at System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController&amp; controller, IControllerFactory&amp; factory) at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&amp; completedSynchronously)</p>
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