I use Entity Framework on my project and I decided to change standard way, which means use - 'using'.
I write my DB layer for communicate Database, but sometimes return this error, please help me to fix this problem:
An exception of type 'System.ObjectDisposedException' occurred in
EntityFramework.SqlServer.dll but was not handled in user code
Additional information: The ObjectContext instance has been disposed
and can no longer be used for operations that require a connection.
Here is my BaseController Code:
//For Data Accsess
public CBEntities DB
{
get
{
return DataAccsesLayer.DbeEntities;
}
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (DataAccsesLayer.DbeEntities != null)
{
DataAccsesLayer.DbeEntities.Dispose();
DataAccsesLayer.DbeEntities = null;
}
}
base.Dispose(disposing);
}
Data project:
//this part of code is member of Data project which is Data Layer
public static class DataAccsesLayer
{
private static CBEntities _context;
public static CBEntities DbeEntities
{
get
{
if (_context == null)
{
_context = new CBEntities();
return _context;
}
else
{
return _context;
}
}
set { _context = value; }
}
}
Related
I am developing an OData API for my Asp.net core application and i want to implement caching on this.
The problem is all my endpoints will be IQueryable with a queryable services with no execution at all. so i can't implement any caching on service level
Controller
public class TagsController : ODataController
{
private readonly ITagService _tagService;
private readonly ILogger<TagsController> _logger;
public TagsController(ITagService tagService, ILogger<TagsController> logger)
{
_tagService = tagService;
_logger = logger;
}
[HttpGet("odata/tags")]
[Tags("Odata")]
[AllowAnonymous]
[EnableCachedQuery]
public ActionResult<IQueryable<Tag>> Get()
{
try
{
return Ok(_tagService.GetAll());
}
catch (Exception ex)
{
_logger.LogError(ex, "Some unknown error has occurred.");
return BadRequest();
}
}
}
So I tried to apply an extension on EnableQuery attribute to add the caching implementation on it. so i added the following
public class EnableCachedQuery : EnableQueryAttribute
{
private IMemoryCache _memoryCache;
public EnableCachedQuery()
{
_memoryCache = new MemoryCache(new MemoryCacheOptions());
}
public override void OnActionExecuting(ActionExecutingContext actionContext)
{
//var url = GetAbsoluteUri(actionContext.HttpContext);
var path = actionContext.HttpContext.Request.Path + actionContext.HttpContext.Request.QueryString;
//check cache
if (_memoryCache.TryGetValue(path, out ObjectResult value))
{
actionContext.Result = value;
}
else
{
base.OnActionExecuting(actionContext);
}
}
public override void OnActionExecuted(ActionExecutedContext context)
{
if (context.Exception != null)
return;
var path = context.HttpContext.Request.Path + context.HttpContext.Request.QueryString;
var cacheEntryOpts = new MemoryCacheEntryOptions().SetAbsoluteExpiration(TimeSpan.FromMinutes(15));
base.OnActionExecuted(context);
_memoryCache.Set(path, context.Result, cacheEntryOpts);
}
}
the first request completed successfully and retrieved the data correctly with filters and queries applied. then when tried to add the data to cache the context.Result holds the ObjectResult and then in the second request which should be cached the value was there but with an error in executing which means that the cached value is not the final output value that should be passed to the Result
Cannot access a disposed context instance. A common cause of this error is disposing a context instance that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling 'Dispose' on the context instance, or wrapping it in a using statement. If you are using dependency injection, you should let the dependency injection container take care of disposing context instances.
Object name: 'ApplicationDbContext'.
============================
Update:
public class ApplicationDbContext : IdentityDbContext<User, Account, Session>, IApplicationDbContext
{
public ApplicationDbContext(
DbContextOptions options,
IApplicationUserService currentUserService,
IDomainEventService domainEventService,
IBackgroundJobService backgroundJob,
IDomainEventService eventService,
IDateTime dateTime) : base(options, currentUserService, domainEventService, backgroundJob, dateTime) { }
public DbSet<Tag> Tags => Set<Tag>();
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
var entityTypes = builder.Model.GetEntityTypes()
.Where(c => typeof(AuditableEntity).IsAssignableFrom(c.ClrType))
.ToList();
foreach (var type in entityTypes)
{
var parameter = Expression.Parameter(type.ClrType);
var deletedCheck = Expression.Lambda
(Expression.Equal(Expression.Property(parameter, nameof(AuditableEntity.Deleted)), Expression.Constant(false)), parameter);
type.SetQueryFilter(deletedCheck);
}
builder.ApplyConfigurationsFromAssembly(typeof(ApplicationDbContext).Assembly);
builder.ApplySeedsFromAssembly(typeof(ApplicationDbContext).Assembly);
}
}
I'm creating a custom model binder for a view model, implementing IModelBinder
I have a lot of properties in my view model, the majority of which do not need any custom binding. Rather than explicitly set all of the property values on my model individually from the ModelBindingContext, I would to be able to get the framework to bind the model for me, then I would carry out any custom binding:
public class ApplicationViewModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
{
throw new ArgumentNullException(nameof(bindingContext));
}
// get .net core to bind values on model
// Cary out any customization of the models properties
bindingContext.Result = ModelBindingResult.Success(bindingContext.Model);
return Task.CompletedTask;
}
}
Basically I want to carry out the default model binding, then apply custom binding, similar to the approach taken in this SO post but for .NET Core, not framework.
I assumed applying the default binding would be straight forward, but haven't been able to find out how to do so. I believe the solution would involve ComplexTypeModelBinder and ComplexTypeModelBinderProvider classes, but can't seem to find out how to go about it.
I know I could just make any changes when the POST request hits my controller method, but this seem the wrong place and wrong time to do so.
For custom ComplexTypeModelBinder, you could inherit from ComplexTypeModelBinder.
Model
public class BinderModel
{
public int Id { get; set; }
public string Name { get; set; }
public string BinderValue { get; set; }
}
Controller Action
[HttpPost]
public void Post([FromForm]BinderModel value)
{
}
CustomBinder
public class CustomBinder : ComplexTypeModelBinder
{
private readonly IDictionary<ModelMetadata, IModelBinder> _propertyBinders;
public CustomBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders)
: base(propertyBinders)
{
_propertyBinders = propertyBinders;
}
protected override Task BindProperty(ModelBindingContext bindingContext)
{
if (bindingContext.FieldName == "BinderValue")
{
bindingContext.Result = ModelBindingResult.Success("BinderValueTest");
return Task.CompletedTask;
}
else
{
return base.BindProperty(bindingContext);
}
}
protected override void SetProperty(ModelBindingContext bindingContext, string modelName, ModelMetadata propertyMetadata, ModelBindingResult result)
{
base.SetProperty(bindingContext, modelName, propertyMetadata, result);
}
}
CustomBinderProvider
public class CustomBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.IsComplexType && !context.Metadata.IsCollectionType)
{
var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
for (var i = 0; i < context.Metadata.Properties.Count; i++)
{
var property = context.Metadata.Properties[i];
propertyBinders.Add(property, context.CreateBinder(property));
}
//var loggerFactory = context.Services.GetRequiredService<ILoggerFactory>();
//return new ComplexTypeModelBinder(propertyBinders, loggerFactory);
return new CustomBinder(propertyBinders);
}
return null;
}
}
Inject provider
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc(options => {
options.ModelBinderProviders.Insert(0, new CustomBinderProvider());
});
}
ComplexTypeModelBinder has unfortunately been deprecated in .Net 5.0, and it's counterpart, ComplexObjectModelBinder, is sealed, so you can't extend from it.
But, you can work around that. ComplexObjectModelBinderProvider is public, and you can use that to create a ComplexObjectModelBinder. Thus, if you make your own custom IModelBinderProvider, you can have the constructor accept a ComplexObjectModelBinderProvider argument, and make use of that to make a ComplexObjectModelBinder. Then, you can pass that to your custom IModelBinder, where it'll happily do its custom work before falling back to the ComplexObjectModelBinder you supplied.
Here's an example. First, your IModelBinder. This example shows that you can use DI if you want to. (In this example, say we needed a DbContext.)
public class MyCustomModelBinder : IModelBinder
{
private readonly IModelBinder _defaultBinder;
private readonly DbContext _dbContext;
public MyCustomModelBinder(IModelBinder defaultBinder, DbContext dbContext)
{
_defaultBinder = defaultBinder;
_dbContext = dbContext;
}
public override Task BindModelAsync(ModelBindingContext bindingContext)
{
// -do custom work here-
return _defaultBinder.BindModelAsync(bindingContext);
}
}
However, in order to use DI on your custom model binder, you'll need a helper class. The problem is, when IModelBinderProvider is called, it won't have access to all the services in a typical request, like your DbContext for example. But this class will help:
internal class DIModelBinder : IModelBinder
{
private readonly IModelBinder _rootBinder;
private readonly ObjectFactory _factory;
public DIModelBinder(Type binderType, IModelBinder rootBinder)
{
if (!typeof(IModelBinder).IsAssignableFrom(binderType))
{
throw new ArgumentException($"Your binderType must derive from IModelBinder.");
}
_factory = ActivatorUtilities.CreateFactory(binderType, new[] { typeof(IModelBinder) });
_rootBinder = rootBinder;
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var requestServices = bindingContext.HttpContext.RequestServices;
var binder = (IModelBinder)_factory(requestServices, new[] { _rootBinder });
return binder.BindModelAsync(bindingContext);
}
}
Now you're ready to write the custom IModelBinderProvider:
public class MyCustomModelBinderProvider : IModelBinderProvider
{
private readonly IModelBinderProvider _rootProvider;
public MyCustomModelBinderProvider(IModelBinderProvider rootProvider)
{
_rootProvider = rootProvider;
}
public IModelBinder? GetBinder(ModelBinderProviderContext context)
{
if (context.Metadata.ModelType == typeof(MyModel))
{
var rootBinder = _rootProvider.GetBinder(context)
?? throw new InvalidOperationException($"Root {_rootProvider.GetType()} did not provide an IModelBinder for MyModel.");
return new DIModelBinder(typeof(MyCustomModelBinder), rootBinder);
}
return null;
}
}
Finally, in your startup file where you configure services, you can grab the ComplexObjectModelBinderProvider instance, use that to create a new instance of your MyCustomModelBinderProvider, and insert that into the ModelBinderProviders.
services.AddMvc(options =>
{
var fallbackProvider = options.ModelBinderProviders
.First(p => p is ComplexObjectModelBinderProvider);
var myProvider = new MyCustomModelBinderProvider(fallbackProvider);
options.ModelBinderProviders.Insert(0, myProvider);
})
I was reading this article and found it quite interesting (thanks #Aaronaught). Was what came closest to solve my problem.
The only detail is that in my case I would use the NHibernate interceptor, but an exception is thrown An unhandled exception of type 'System.StackOverflowException' occurred in System.Core.dll
Code
Session factory:
public class SessionFactoryBuilder : IProvider
{
private ISessionFactory _sessionFactory;
private readonly Configuration _configuration;
public SessionFactoryBuilder(AuditInterceptor auditInterceptor)
{
_configuration = Fluently.Configure(new Configuration().Configure())
.Mappings(m => m.AutoMappings.Add(AutoMap.AssemblyOf<IEntidade>(new AutomappingConfiguration())))
.ExposeConfiguration(SetupDatabase)
.BuildConfiguration();
_configuration.SetInterceptor(auditInterceptor);
_sessionFactory = _configuration.BuildSessionFactory();
}
private static void SetupDatabase(Configuration config)
{
var schema = new SchemaExport(config);
//schema.Execute(true, true, false);
}
public object Create(IContext context)
{
return _sessionFactory;
}
public Type Type
{
get { return typeof(ISessionFactory); }
}
}
I have a module that sets up my repositories and ORM (NHibernate)
public class RepositoriosModule : NinjectModule
{
public override void Load()
{
Bind<AuditInterceptor>().ToSelf().InRequestScope();
// NHibernate
Bind<ISessionFactory>().ToProvider<SessionFactoryBuilder>().InSingletonScope();
Bind<ISession>().ToMethod(CreateSession).InRequestScope();
Bind<NHUnitOfWork>().ToSelf().InRequestScope();
//Model Repositories
Bind<IRepositorio<Usuario>, IUsuariosRepositorio>().To<UsuariosRepositorio>().InRequestScope();
}
private ISession CreateSession(IContext context)
{
return context.Kernel.Get<ISessionFactory>().OpenSession();
}
}
Interceptor to update auditable properties (CriadoEm (create at), CriadoPor (create by), AtualizadoEm and AtualizadoPor)
public class AuditInterceptor : EmptyInterceptor
{
private readonly IUsuario _usuarioLogado;
public AuditInterceptor(IUsuario usuarioLogado)
{
_usuarioLogado = usuarioLogado;
}
public override bool OnFlushDirty(object entity, object id, object[] currentState, object[] previousState, string[] propertyNames, NHibernate.Type.IType[] types)
{
var auditableObject = entity as IAuditavel;
if (auditableObject != null)
{
currentState[Array.IndexOf(propertyNames, "AtualizadoEm")] = DateTime.Now;
return true;
}
return false;
}
public override bool OnSave(object entity, object id, object[] state, string[] propertyNames, NHibernate.Type.IType[] types)
{
var auditableObject = entity as IAuditavel;
if (auditableObject != null)
{
var currentDate = DateTime.Now;
state[Array.IndexOf(propertyNames, "CriadoEm")] = currentDate;
return true;
}
return false;
}
}
A provider to retrieve the logged in user:
public class UsuarioProvider : Provider
{
private Usuario _usuario;
protected override Usuario CreateInstance(IContext context)
{
var usuariosRepositorio = context.Kernel.Get<IUsuariosRepositorio>(); // Stackoverflow on this line!!
if (_usuario == null && WebSecurity.IsAuthenticated)
_usuario = usuariosRepositorio.Get(WebSecurity.CurrentUserId);
return _usuario;
}
}
And the class NinjectWebCommon (web application) define:
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<IUsuario>().ToProvider<UsuarioProvider>().InRequestScope(); //.When((req) => WebSecurity.IsAuthenticated)
kernel.Load(new RepositoriosModule(), new MvcSiteMapProviderModule());
}
[Add] Repository class
public class UsuariosRepositorio : Repositorio<Usuario>, IUsuariosRepositorio
{
public UsuariosRepositorio(NHUnitOfWork unitOfWork)
: base(unitOfWork)
{ }
}
public class Repositorio<T> : IRepositorio<T>
where T : class, IEntidade
{
private readonly NHUnitOfWork _unitOfWork;
public IUnitOfWork UnitOfWork { get { return _unitOfWork; } }
private readonly ISession _session;
public Repositorio(IUnitOfWork unitOfWork)
{
_unitOfWork = (NHUnitOfWork)unitOfWork;
_session = _unitOfWork.Context.SessionFactory.GetCurrentSession();
}
public void Remover(T obj)
{
_session.Delete(obj);
}
public void Armazenar(T obj)
{
_session.SaveOrUpdate(obj);
}
public IQueryable<T> All()
{
return _session.Query<T>();
}
public object Get(Type entity, int id)
{
return _session.Get(entity, id);
}
public T Get(Expression<Func<T, bool>> expression)
{
return Query(expression).SingleOrDefault();
}
public T Get(int id)
{
return _session.Get<T>(id);
}
public IQueryable<T> Query(Expression<Func<T, bool>> expression)
{
return All().Where(expression);
}
}
Problem
The problem occurs in the class UsuarioProvider while trying to retrieve the user repository.
Stackoverflow error:
An unhandled exception of type 'System.StackOverflowException' occurred in System.Core.dll
I see two problems :
The main problem I see is that SessionFactoryBuilder needs an AuditInterceptor which needs an IUsuario, which needs a UsuarioProvider, which needs a SessionFactoryBuilder, thus introducing a cycle, and a stack-overflow.
The second problem I see is that your AuditInterceptor is linked to a request when your SessionFactoryBuilder is singleton like. I must confess I can't see how it work with several logged users.
You should instantiate and attach the AuditInterceptor as part of the CreateSession, instead of trying to create it once and for all as part of the Session builder. Once this is done, your interceptor should not rely on a Session that needs an AuditInterceptor as part of its creation (you may need a separate Session creation mechanism for that. A stateless Session might do the trick)
I'm developing a MVC4 app using .Net4.5, EF5 and MSSQL 2008R2. I'm using Db Context and autogenerated entity classes/models and the Unit of Work pattern.
When I attempt to update a table record through the Edit ActionResult method, the record gets deleted when I data updated was originally null, like adding a middle name for example.
I can follow the object from the ActionResult to the GenericRepository to the UnitOfWork Save() where the db context savechanges() is called. The data is there until then. After that, I'm not sure how to debug it.
So, any help with either debugging or with resolving this would be appreciated. I can successfully create and delete table records. I also tried simply using the db context in the Edit ActionResult with the same delete results. I tested the mapped stored procedure, which updated correctly.
[HttpPost]
public ActionResult Edit(v_Demographics vm)
{
try
{
if (ModelState.IsValid)
{
unitOfWork.DemographicsRepository.Update(vm);
unitOfWork.Save();
//db.Entry(vm).State = EntityState.Modified;
//db.SaveChanges();
return RedirectToAction("Index");
}
}
catch (DataException)
{
//Log the error (add a variable name after DataException)
ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
}
return View(vm);
}
public class GenericRepository<TEntity> where TEntity : class
{
internal SEntities db = new SEntities();
internal DbSet<TEntity> dbSet;
public GenericRepository(AIPIMSEntities db)
{
this.db = db;
this.dbSet = db.Set<TEntity>();
}
public virtual void Update(TEntity entityToUpdate)
{
dbSet.Attach(entityToUpdate);
db.Entry(entityToUpdate).State = EntityState.Modified;
}
}
public class UnitOfWork : IDisposable
{
private AIPIMSEntities db = new AIPIMSEntities();
private GenericRepository<v_Demographics> demographicsRepository;
public GenericRepository<v_Demographics> DemographicsRepository
{
get
{
if (this.demographicsRepository == null)
{
this.demographicsRepository = new GenericRepository<v_Demographics>(db);
}
return demographicsRepository;
}
}
public void Save()
{
db.SaveChanges();
}
private bool disposed = false;
protected virtual void Dispose(bool disposing)
{
if (!this.disposed)
{
if (disposing)
{
db.Dispose();
}
}
this.disposed = true;
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
As it turns out, the delete error was caused by a MSSQL view. The code here is based upon this tutorial, and works very now.
I'm creating an Asp.Net MVC 3 application with NHibernate as my ORM. In my my edit action method I call the Save method in my DatabaseAccessObject class, but instead of updating the object it creates a new one. I can't figure out why.
Here's the code for the method that returns my configured SessionFactory, and my global.asax.cs file where I'm storing the SessionFactory:
public static ISessionFactory CreateSessionFactory()
{
return Fluently.Configure()
.Database(MsSqlConfiguration.MsSql2008.ConnectionString("Server=(local);Database=WebApplicationPbiBoard;Trusted_Connection=True;"))
.Mappings(m => m.FluentMappings.AddFromAssemblyOf<WebApplicationPbiBoard.Models.ScrumModels_Mappings.PbiMap>())
.ExposeConfiguration(cfg => new SchemaUpdate(cfg).Execute(false, true))
.CurrentSessionContext("web")
.BuildSessionFactory();
}
public class MvcApplication : System.Web.HttpApplication
{
public static ISessionFactory SessionFactory { get; private set; }
protected void Application_Start()
{
//my additions
SessionFactory = NHibernateConfigurator.CreateSessionFactory();
}
protected void Application_OnEnd()
{
SessionFactory.Dispose();
}
protected void Application_BeginRequest()
{
ISession session = SessionFactory.OpenSession();
CurrentSessionContext.Bind(session);
}
protected void Application_EndRequest()
{
CurrentSessionContext.Unbind(SessionFactory);
}
}
Here's the relevant snippet from my DataAccessObject, which simply wraps NHibernate CRUD operations:
public class DatabaseAccessObject<T> where T : class
{
private readonly ISession session = MvcApplication.SessionFactory.GetCurrentSession();
private ISession Session { get { return session; } }
public T Save(T obj)
{
ITransaction transaction = null;
try
{
transaction = Session.BeginTransaction();
Session.SaveOrUpdate(obj);
transaction.Commit();
return obj;
}
catch (Exception ex)
{
if (transaction != null && transaction.IsActive)
transaction.Rollback();
throw;
}
}
And finally, here's the code for my Http-Post edit method:
private readonly DatabaseAccessObject<Sprint> db = new DatabaseAccessObject<Sprint>();
private DatabaseAccessObject<Sprint> Db { get { return db; } }
[HttpPost]
public ActionResult Edit(Sprint editedSprint)
{
if (ModelState.IsValid)
{
Db.Save(editedSprint);
return RedirectToAction("Index");
}
else
return View(editedSprint);
}
Any help would be appreciated.
The object you're saving probably hasn't got the Id set on it.
SaveOrUpdate does one of two things:
- Update() if the Id is set.
- Save() if the Id is not set.
refer to the docs:
http://www.nhforge.org/doc/nh/en/index.html