c# - Entity Framework 代码优先与 T4 模板

Question

我将使用如下文所述的 T4 模板创建代码优先 View :

Article here

但它造成了

run time exception

如下图。这是为什么？

我的连接字符串已在 App.config 中正确配置。

我的应用程序是基于 N 层的。因此 DbContext 驱动类位于数据层。

这是我的连接字符串:

<add name="PawLoyalty" connectionString="Server=.;database=PawLoyalty;Trusted_connection=true;pooling=true;MultipleActiveResultSets=True" providerName="System.Data.SqlClient" />

我在 vs 2010 中使用 EF 4.1。

Running transformation: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.ArgumentException: The argument 'nameOrConnectionString' cannot be null, empty or contain only white space.

at System.Data.Entity.ModelConfiguration.Utilities.RuntimeFailureMethods.ReportFailure(ContractFailureKind contractFailureKind, String userMessage, String conditionText, Exception innerException)
at System.Data.Entity.DbContext..ctor(String nameOrConnectionString)
at PawLoyalty.Data.DataCatalog..ctor(Boolean allowLazyLoading) in D:\My Blog\Test Projects\PawLoyalty\PawLoyalty\PawLoyalty.Data\DataCatalog.cs:line 31
at PawLoyalty.Data.DataCatalog..ctor() in D:\My Blog\Test Projects\PawLoyalty\PawLoyalty\PawLoyalty.Data\DataCatalog.cs:line 26
--- End of inner exception stack trace ---
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.Activator.CreateInstance(Type type)
at Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.GetEdmx(Type contextType)
at Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.GenerateViews(String contextTypeName)
at Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.TransformText()
at Microsoft.VisualStudio.TextTemplating.TransformationRunner.RunTransformation(TemplateProcessingSession session, String source, ITextTemplatingEngineHost host, String& result)

已更新

我的 DbContext 派生类如下所示。

 [Export(typeof(ISecurityDataCatalog))]
    [Export(typeof(IMappingDataCatalog))]
    [Export(typeof(IPawLoyaltyDataCatalog))]
    [PartCreationPolicy(CreationPolicy.NonShared)]
    public class DataCatalog : DbContext, IPawLoyaltyDataCatalog, ISecurityDataCatalog, IMappingDataCatalog
    {

        public static string ConnectionString { get; set; }
        public static string AccountToken { get; set; }

        public DataCatalog()
            : this(false)
        {
        }

        public DataCatalog(bool allowLazyLoading = false)
            : base(ConnectionString)
        {
            Configuration.LazyLoadingEnabled = allowLazyLoading;
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.ComplexType<DiscountValue>().Property(d => d.Fixed).HasPrecision(18, 2);
            modelBuilder.ComplexType<DiscountValue>().Property(d => d.Percentage).HasPrecision(18, 4);
            modelBuilder.Entity<InvoiceFee>().Property(d => d.Fixed).HasPrecision(18, 2);
            modelBuilder.Entity<InvoiceFee>().Property(d => d.Percentage).HasPrecision(18, 4);
            modelBuilder.Entity<InvoiceFee>().Property(d => d.Total).HasPrecision(18, 4);
            modelBuilder.Entity<Invoice>().Property(d => d.Discount).HasPrecision(18, 2);
            modelBuilder.Entity<Invoice>().HasRequired(i => i.Appointment).WithOptional(a => a.Invoice).WillCascadeOnDelete(false);
            modelBuilder.Entity<InvoiceItem>().Property(d => d.Price).HasPrecision(18, 2);
            modelBuilder.Entity<InvoiceItem>().Property(d => d.LatestTotal).HasPrecision(18, 2);
            modelBuilder.Entity<InvoiceItem>().HasRequired(i => i.Allocation).WithOptional(a => a.InvoiceItem).WillCascadeOnDelete(false);
            modelBuilder.Entity<InvoicePayment>().Property(d => d.Amount).HasPrecision(18, 4);
            modelBuilder.Entity<ServicePrice>().Property(d => d.Price).HasPrecision(18, 2);
            modelBuilder.Entity<ServiceBreedPrice>().Property(d => d.Price).HasPrecision(18, 2);
            modelBuilder.Entity<ProviderPolicy>().Property(d => d.SalesTax).HasPrecision(18, 4);
            modelBuilder.Entity<ProviderCredit>().Property(d => d.Balance).HasPrecision(18, 2);
            modelBuilder.Entity<CombinedServiceDiscountDefinition>().HasRequired(c => c.PrimaryService).WithMany().WillCascadeOnDelete(false);
            modelBuilder.Entity<CombinedServiceDiscountDefinition>().HasRequired(c => c.SecondaryService).WithMany().WillCascadeOnDelete(false);

            modelBuilder.Entity<MedicalRecord>().HasRequired(m => m.Pet).WithOptional(p => p.Medical).WillCascadeOnDelete(false);
            modelBuilder.Entity<BehavioralRecord>().HasRequired(b => b.Pet).WithOptional(p => p.Behavioral).WillCascadeOnDelete(false);
            modelBuilder.Entity<DietRecord>().HasRequired(d => d.Pet).WithOptional(p => p.Diet).WillCascadeOnDelete(false);

            modelBuilder.Entity<Provider>().HasOptional(p => p.Profile).WithRequired(p => p.Provider).WillCascadeOnDelete(true);

            modelBuilder.Entity<ProviderProfile>().HasOptional(p => p.Policy).WithRequired(p => p.Profile).WillCascadeOnDelete(true);
            modelBuilder.Entity<ProviderProfile>().HasOptional(p => p.CustomerRequirements).WithRequired(p => p.Profile).WillCascadeOnDelete(true);
            modelBuilder.Entity<ProviderProfile>().HasOptional(p => p.PaymentProfile).WithRequired(p => p.Profile).WillCascadeOnDelete(true);

            modelBuilder.Entity<Resource>().HasMany(r => r.Availability).WithRequired(a => a.Resource).WillCascadeOnDelete(true);

            Database.SetInitializer<DataCatalog>(null);
            base.OnModelCreating(modelBuilder);
        }

        public const string ServiceKey = "PawLoyalty";

        public DbSet<StreetAddress> StreetAddresses { get; set; }
        public DbSet<Appointment> Appointments { get; set; }
        public DbSet<Invoice> Invoices { get; set; }
        public DbSet<InsuranceCarrier> InsuranceCarriers { get; set; }
        public DbSet<PromotionCode> PromotionCodes { get; set; }

        // Provider Classes
        public DbSet<Provider> Providers { get; set; }
        public DbSet<ProviderProfile> ProviderProfiles { get; set; }
        //public DbSet<ProviderResourceItem> ProviderResourceItems { get; set; }
        public DbSet<Allocation> ResourceAllocations { get; set; }
        public DbSet<ResourceAvailability> ResourceAvailabilities { get; set; }
        public DbSet<Resource> Resources { get; set; }

        /// <summary>
        /// Wraps the object context detach method
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        public void Detach<T>(T t) where T : class
        {
            // TODO: Is this needed? Hidden behind an interface in CTP5 implying infrequent usage.
            ((IObjectContextAdapter)this).ObjectContext.Detach(t);
        }

        // Owner Classes
        public DbSet<MedicalRecordOrder> Orders { get; set; }
        public DbSet<Owner> Owners { get; set; }
        public DbSet<Pet> Pets { get; set; }
        public DbSet<Breed> Breeds { get; set; }
        public DbSet<PetProvider> PetProviders { get; set; }

        // Security Catalog Items
        public DbSet<User> Users { get; set; }

        // Bing Maps Catalog items
        public DbSet<KnownLocation> KnownLocations { get; set; }
        public DbSet<KnownPostalCode> KnownPostalCodes { get; set; }

        public DbSet<QueuedEmail> QueuedEmails { get; set; }
        public DbSet<InvoicePayment> InvoicePayments { get; set; }
        public DbSet<Employee> Employees { get; set; }
        public DbSet<Schedule> Schedules { get; set; }
        public DbSet<Subscription> Subscriptions { get; set; }
        public DbSet<EmailSubscription> EmailSubscriptions { get; set; }

        public DbSet<ResourceAvailabilityUpdate> ResourceAvailabilityUpdates { get; set; }
        public DbSet<EmployeeAvailabilityUpdate> EmployeeAvailabilityUpdates { get; set; }
        public DbSet<InvoiceConfiguration> InvoiceConfigurations { get; set; }

        public DbSet<Vaccine> Vaccines { get; set; }
        public DbSet<TourEmail> TourEmails { get; set; }
        public DbSet<ReservationRequest> ReservationRequest { get; set; }
        //public DbSet<ReservationRequestPets> ReservationRequestPets { get; set; }
        public DbSet<Vaccination> Vaccinations { get; set; }
        public DbSet<SpecialInstruction> SpecialInstructions { get; set; }

        public DbSet<Product> Products { get; set; }
        public DbSet<ProductCategory> ProductCategories { get; set; }
        public DbSet<VendorStock> VendorStocks { get; set; }
        public DbSet<ShoppingCart> ShoppingCarts { get; set; }
        public DbSet<SaleDetail> SaleDetails { get; set; }
        public DbSet<Sale> Sales { get; set; }
        public DbSet<SalePayment> SalePayments { get; set; }

        public DbSet<PetService> PetServices { get; set; }
        public DbSet<PetServicePrice> PetServicePrices { get; set; }

        public DbSet<MiscProperty> MiscProperties { get; set; }
        public DbSet<ProviderMiscProperty> ProviderMiscProperties { get; set; }

        public DbSet<ProviderAuthorizedCreditCard> ProviderAuthorizedCreditCards { get; set; }
        public DbSet<AuthorizedCreditCard> AuthorizedCreditCards { get; set; }
        public DbSet<ProviderPackage> ProviderPackages { get; set; }

        public DbSet<ProviderEmailPreference> ProviderEmailPreferences { get; set; }
        public DbSet<EmailType> EmailTypes { get; set; }

        public DbSet<RetailSaleReturn> RetailSaleReturns { get; set; }
        public DbSet<ServiceRefund> ServiceRefunds { get; set; }

    }

Answer 1

问题是 DbContext 派生类的 (DataCatalog) 无参数构造函数连接字符串问题。

在 @Pawel 的支持下，我解决了我的问题。 您只需要为无参数构造函数提供连接字符串，如下所示。

 public class DataCatalog : DbContext
    {
        public static string ConnectionString { get; set; }

        public DataCatalog() : base(ConnectionString ?? "PawLoyalty")
        {

        }  
    }

注意 1:如果您在单独的层(类库项目)中，则必须在 App.Config 文件中提供连接字符串。

注意 2:完成所有更改后，您必须编译您的项目，然后再次运行 T4 模板

希望这对将来的人有所帮助。