Question

我是基于Autofac的依赖项注入的新手。根据我们公司的要求，我必须在要创建的新Web API中使用它。以下是我的代码。我在Autofac中使用IocConfig类在Web API中创建和注入对象。

public class MemberCodeController : ApiController
{
    private IMemberStrategy memberStrategy;
    private IMemberDetail memberDetail;

    //Constructor dependency injection through Autofac
    public MemberCodeController(IMemberStrategy memberStrategy, 
              IMemberDetail memberDetail)
    {
        this.memberStrategy = memberStrategy;
    }

public IHttpActionResult CreateMember(string email)
    {
         memberDetail.DataFields.RegisterCode  = GetCode();
         memberDetail.Email = email;
    }
}

The MemberDetail class:

public interface IMemberDetail
{
  String Email { get; set; }
  DataFields DataFields { get; set; }
}

public class MemberDetail : IMemberDetail
{     
  public String Email { get; set; }
  public DataFields DataFields { get; set; }
}

public interface IDataFields
{
  String RegisterCode { get; set; }
}
public class DataFields : IDataFields
{
  public String RegisterCode { get; set; }
}

IocConfig：

public class IocConfig
{
    //Autofac configuration
    public static void Configure()
    {
        ContainerBuilder builder = new ContainerBuilder();
        builder.RegisterApiControllers(Assembly.GetExecutingAssembly());           
        builder.RegisterType<MemberStrategy>().As<IMemberStrategy>();
        builder.RegisterType<DataFields>().As<IDataFields>();
        builder.RegisterType<MemberDetail>().As<IMemberDetail>();
        IContainer container = builder.Build();
        AutofacWebApiDependencyResolver resolver = new 
        AutofacWebApiDependencyResolver(container);
        GlobalConfiguration.Configuration.DependencyResolver = resolver;
    }
}

我遇到的问题是，当我尝试使用此行时， memberDetail.DataFields.RegisterCode = GetCode（）; DataFields为空。显然，Autofac在构造MemberDetail对象时并未创建它。

Answer 1

MemberDetail在其构造函数中未显示对IDataField的依赖。

因此Autofac不会为此依赖关系创建实例。

添加这样的依赖项将注入一个实例：

public class MemberDetail : IMemberDetail
{     
  public String Email { get; set; }
  public IDataFields DataFields { get; set; }

  public MemberDetail(IDataFields dataFields)
  {
    DataFields = dataFields;
  }
}

我也将DataFields成员类型更改为IDataFields，以建立对接口的依赖。

Answer 2

MemberDetail对象已正确创建。您缺少的是DataFields属性的初始化。将构造函数添加到DataFields类并在那里初始化DataFields属性，您的问题将消失。

Autofac无法成功创建复杂对象

2 个答案: