c# - AutoFac DbContext 问题 - 在创建模型时无法使用

Question

我在开始使用 AutoFac 和 IoC 时遇到了一些问题。我们有一个可用的应用程序，但是我是从头开始使用这个应用程序的，看不出两者之间的区别。

我正在使用一个简单的 AJAX 页面对此进行测试，该页面通过 ServiceStack API 调用服务层。当使用 MockRepositories 时，这工作正常，所以我知道事情的那一面正在工作。

然而，当我用使用 Entity Framework 的模拟替换模拟时，尽管所有注册看起来都是正确的并且有效，但我收到错误“创建模型时无法使用上下文。”

我在下面包含了我的代码:

public class SomeObject
{
    public int Id { get; set; }
}



public class IoCExampleContext : DbContext, IIoCExampleContext
{

    public IDbSet<SomeObject> SomeObjects { get; set; }

    static IoCExampleContext()
    {
        Database.SetInitializer(new IoCExampleDatabaseInitilizer());
    }

    public IoCExampleContext(string connectionStringName)
        : base(connectionStringName)
    {
        Configuration.ProxyCreationEnabled = false;
    }

    public IoCExampleContext()
        : this("name=IoCExample")
    {}


    public string ConnectionString
    {
        get { return Database.Connection.ConnectionString; }
    }


    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        BuildModels(modelBuilder);
    }

    private void BuildModels(DbModelBuilder builder)
    {
        var typeToUse = typeof(SomeObjectModelBuilder);
        var namespaceToUse = typeToUse.Namespace;

        var toReg = Assembly
                        .GetAssembly(typeToUse)
                        .GetTypes()
                        .Where(type => type.Namespace != null && type.Namespace.StartsWith(namespaceToUse))
                        .Where(type => type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));

        foreach (object configurationInstance in toReg.Select(Activator.CreateInstance))
        {
            builder.Configurations.Add((dynamic)configurationInstance);
        }
    }
}



public class IoCExampleDatabaseInitilizer : CreateDatabaseIfNotExists<IoCExampleContext>
{
    protected override void Seed(IoCExampleContext context)
    {
    }
}



public interface IRepository<TEntity> where TEntity : class
{
    IQueryable<TEntity> GetQuery();
    IEnumerable<TEntity> GetAll();
    IEnumerable<TEntity> Where(Expression<Func<TEntity, bool>> predicate);

    // ...Various "standard" CRUD calls
}



public class GenericRepository<TEntity> : IRepository<TEntity> where TEntity : class
{
    protected DbContext _context;
    private readonly DbSet<TEntity> _dbSet;

    public GenericRepository(DbContext context)
    {
        _context = context;
        _dbSet = _context.Set<TEntity>();
    }

    public IQueryable<TEntity> GetQuery()
    {
        return _dbSet;
    }

    public IEnumerable<TEntity> GetAll()
    {
        return GetQuery().AsEnumerable();
    }

    public IEnumerable<TEntity> Where(Expression<Func<TEntity, bool>> predicate)
    {
        return GetQuery().Where(predicate);
    }

    // ...Various "standard" CRUD calls

    public void Dispose()
    {
        OnDispose(true);
    }

    protected void OnDispose(bool disposing)
    {
        if (disposing)
        {
            if (_context != null)
            {
                _context.Dispose();
                _context = null;
            }
        }
    }
}


public class DependencyBootstrapper
{
    private ContainerBuilder _builder;

    public IContainer Start()
    {
        _builder = new ContainerBuilder();
        _builder.RegisterFilterProvider();
        RegisterControllers();
        return _builder.Build();
    }

    private void RegisterControllers()
    {
        RegisterAssembly(Assembly.GetExecutingAssembly());
        _builder.RegisterModelBinderProvider();

        RegisterPerLifetimeConnections();
        RegisterRepositories();
        RegisterServices();
    }

    private void RegisterAssembly(Assembly assembly)
    {
        _builder.RegisterModelBinders(assembly);
        _builder.RegisterControllers(assembly);
    }

    private void RegisterRepositories()
    {
        _builder.RegisterGeneric(typeof(GenericRepository<>)).As(typeof(IRepository<>)); 
        _builder.RegisterType<GenericRepository<SomeObject>>().As<IRepository<SomeObject>>();
        //... More registrations
    }

    private void RegisterServices()
    {
        _builder.RegisterType<SomeObjectService>().As<ISomeObjectService>();
        //... More registrations
    }

    private void RegisterPerLifetimeConnections()
    {
        const string connectionStringName = "IoCExample";
        _builder.RegisterType<IoCExampleContext>()
            .As<DbContext>()
            .WithParameter("connectionStringName", connectionStringName)
            .InstancePerLifetimeScope();

        _builder.Register(c => new HttpContextWrapper(HttpContext.Current))
            .As<HttpContextBase>();
    }
}

我不知道它是否相关，但由于我们无法访问 global.asax 方法，我们通过 PreApplicationStartMethod.OnPreApplicationStart 调用 Bootstrap (据我所知，与 Application_Start 几乎相同)。

有点担心的是，当我在连接字符串上启用多个事件结果集时它起作用了——这向我暗示我注册的 DbContext 不正确并且它跨越多个上下文。

谁能发现我哪里出错了？

Answer 1

连接字符串是问题所在。确保您已在 web/app.comfig 中正确设置它。