我在Visual Studion 2013 Express for Web中使用ASP.Net MVC模板创建了一个简单的项目.它不使用任何身份验证.然后我安装了EntityFramework(v6.0.1),EntityFramework.sqlServerCompact包.
我的DbContext类非常简单：
public class EditTestContext : DbContext
{
public EditTestContext() : base("EditTestContext")
{
}
public EditTestContext(string connectionString) : base(connectionString)
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
Database.SetInitializer(
new DropCreateDatabaseIfModelChanges<EditTestContext>());
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
modelBuilder.Configurations.Add(new EditTestConfig());
}
}
实际的上下文对象是在Unit of Work类中创建的：
public class EditTestUoW:IEditTestUoW,IDisposable
{
private DbContext dbContext;
public EditTestUoW()
{
CreateDbContext();
}
private void CreateDbContext()
{
dbContext = new EditTestContext();//NEW DBCONTEXT OBJECT IS CREATED
dbContext.Configuration.LazyLoadingEnabled = false;
dbContext.Configuration.ProxyCreationEnabled = false;
dbContext.Configuration.ValidateOnSaveEnabled = false;
}
public IRepository<EditTestModel> EditTestRepo
{
get
{
return new EFRepository<EditTestModel>(dbContext);
}
}
}
使用的连接字符串是：
<add name="EditTestContext" connectionString="Data Source=
|DataDirectory|EditTestDb.sdf;Max Database Size=256;
Max Buffer Size=1024;File Mode=Shared Read;
Persist Security Info=False;" providerName="System.Data.sqlServerCe.4.0" />
现在,当我尝试使用此上下文访问任何内容时：
var rep=UoW.EditTestRepo; var list=rep.GetAll().ToList();
我在rep.GetAll()函数上遇到以下异常：
System.InvalidOperationException：Sequence不包含匹配元素
在深入挖掘时,Repository类(DbSet< EditTest>)中的IQueryable抛出以下异常：
The context cannot be used while the model is being created. This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. Note that instance members of DbContext and related classes are not guaranteed to be thread safe.
我认为它可能是由ninject造成的,但即使在我删除它之后它仍然存在.
我在这里做错了什么(某些装配参考等)丢失了？
解决方法
在经过一番其他搜索后,我得到了
this MSDN论坛链接.正如Rowan所建议的那样,我尝试使用EFRepository类中的以下语句手动初始化上下文：
dbContext.Database.Initialize(false);
应用程序在访问GetAll()方法之前失败了.但这暴露了堆栈跟踪,这给了我一些方向：
[InvalidOperationException: Sequence contains no matching element]
System.Linq.Enumerable.Single(IEnumerable`1 source,Func`2 predicate) +2614017
System.Data.Entity.Utilities.DbProviderManifestExtensions.GetStoreTypeFromName
(DbProviderManifest providerManifest,String name) +146
.....Other Lines.....
System.Data.Entity.Internal.InternalContext.Initialize() +31
System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType
(Type entityType) +38
System.Data.Entity.Internal.Linq.InternalSet`1.Initialize() +138
System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext() +38
System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable
.get_Provider() +99
System.Linq.Queryable.Any(IQueryable`1 source) +50
然后搜索DbProviderManifestExtensions.GetStoreTypeFromName显示这是EF试图获取列类型的行.我为我的Id列指定了UNIQUEIDENTIFIER：
Property(x=> x.Id).HasColumnType("UNIQUEIDENTIFIER")
一旦我对此发表评论,一切都很顺利.
