我将使用T4模板创建代码优先视图，如下文所述：
但它导致
运行时异常
如下。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" />
我正在使用EF 4.1和vs 2010。
正在运行转换：System.Reflection.TargetInvocationException：抛出了异常 通过调用的目标。
---＆GT; System.ArgumentException：参数'nameOrConnectionString'不能为null，为空或仅包含空格。at System.Data.Entity.ModelConfiguration.Utilities.RuntimeFailureMethods.ReportFailure（ContractFailureKind contractFailureKind，String userMessage，String conditionText， 异常innerException）
在System.Data.Entity.DbContext..ctor（String nameOrConnectionString）
在D：\ My Blog \ Test中的PawLoyalty.Data.DataCatalog..ctor（Boolean allowLazyLoading） Projects \ PawLoyalty \ PawLoyalty \ PawLoyalty.Data \ DataCatalog.cs：第31行
在D：\ My Blog \ Test Projects \ PawLoyalty \ PawLoyalty \ PawLoyalty.Data \ DataCatalog.cs：第26行的PawLoyalty.Data.DataCatalog..ctor（）中 ---内部异常堆栈跟踪结束---
在System.RuntimeTypeHandle.CreateInstance（RuntimeType类型，Boolean publicOnly，Boolean noCheck，Boolean＆amp; canBeCached， RuntimeMethodHandleInternal＆安培; ctor，布尔＆amp; bNeedSecurityCheck）
在System.RuntimeType.CreateInstanceSlow（Boolean publicOnly，Boolean skipCheckThis，Boolean fillCache，StackCrawlMark＆amp; stackMark）
在System.RuntimeType.CreateInstanceDefaultCtor（Boolean publicOnly，Boolean skipCheckThis，Boolean fillCache，StackCrawlMark＆amp; stackMark）
在System.Activator.CreateInstance（Type type，Boolean nonPublic）
在System.Activator.CreateInstance（类型类型）
在Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.GetEdmx（类型 contextType）
在Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.GenerateViews（String contextTypeName）
在Microsoft.VisualStudio.TextTemplatingD6E95B37BD0790EBBCC7DB570AD3E2AC.GeneratedTextTransformation.TransformText（）
在Microsoft.VisualStudio.TextTemplating.TransformationRunner.RunTransformation（TemplateProcessingSession） session，String source，ITextTemplatingEngineHost host，String＆amp; 结果）
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; }
}
答案 0 :(得分：7)
问题是DbContext派生类（DataCatalog）参数减去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。 您只需要为参数较少的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1：如果您在单独的图层（类库项目）中，则必须在 App.Config 文件中提供连接字符串。
注2：完成所有更改后，您必须编译您的项目再次运行T4模板
希望这将有助于将来的某些人。
答案 1 :(得分：1)
我只根据你的错误代码写这个。您的错误代码显示：
参数'nameOrConnectionString'不能为null，为空或包含 只有白色空间。
所以你的connection string有错误。检查web config中的连接字符串。确保连接字符串没有空格。