DbContext没有在ASP.Net MVC中使用SQL Server Compact进行初始化

Question

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,IQueryable从Repository class(DbSet<EditTest>)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.

我以为它可能是由ninject它引起的,但是在我删除之后它仍然存在.

我在这里做错了什么(某些装配参考等)丢失了？

Answer 1

在对该问题进行了一些其他搜索之后,我得到了这个 MSDN论坛链接.正如Rowan所建议的那样,我尝试使用我的EFRepository类中的以下语句手动初始化上下文:

dbContext.Database.Initialize(false);

应用程序在访问该方法之前失败了GetAll().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试图获得列类型的行.我已UNIQUEIDENTIFIER为我的Id列指定:

Property(x=> x.Id).HasColumnType("UNIQUEIDENTIFIER")

一旦我对此发表评论,一切都很顺利.

虽然Codeplex上有一个请求,以便在列类型对数据库提供程序无效时提供正确的错误消息.