创建 MVC Web API 时出现“InvalidOperationException”异常答案

【问题标题】："InvalidOperationException" Exceptions while Creating MVC Web API创建 MVC Web API 时出现“InvalidOperationException”异常
【发布时间】：2016-10-25 04:08:07
【问题描述】：

我正在尝试使用存储库模式创建 MVC API。以下是我的代码

IInsurerDAL.cs

namespace InformationServices.DAL
{
    public interface IInsurerDAL
    {
        Task<DataTable> GetInsurer(string cover,string version);
    }
}

InsurerDAL.cs

namespace InformationServices.DAL
{
    public class InsurerDAL : IInsurerDAL
    {
        int commandTimeout;

    public InsurerDAL()
    {
        Int32.TryParse(ConfigurationManager.AppSettings["CommandTimeout"], out commandTimeout);
        if (commandTimeout <= 0)
        {
            commandTimeout = 30;
        }
    }
    public async Task<DataTable> GetInsurer(string cover, string version)
    {
                //some code 
    }    
    }
}

IInsurerRepository.cs

namespace InformationServices.Repository
{
    public interface IInsurerRepository
    {
        ConsumerDetails ConsumerDetails { get; set; }
        Task<ResponseModel<Insurer>> GetInsurer(string cover, string version);
    }
}

InsurerRepository.cs

namespace InformationServices.Repository
{
    public class InsurerRepository : IInsurerRepository, IDisposable
    {
        InsurerDAL oInsurerDAL;
        ConsumerDetails oConsumerDetails { get; set; }

        public ConsumerDetails ConsumerDetails
        {
            get
            {
                return oConsumerDetails;
            }
            set
            {
                oConsumerDetails = value;
            }
        }

        public InsurerRepository()
        {
            var container = new UnityContainer();
            oInsurerDAL = container.Resolve<InsurerDAL>();

            MapperRegistry.Mappers.Add(new DataReaderMapper());

            //To load the DataReaderMapper before we actually use it.
            var type = typeof(DataReaderMapper);
        }
        public async Task<ResponseModel<Insurer>> GetInsurer(string cover, string version)
        {

        }
        //Implementation of IDisposable interfase.
        protected void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (oInsurerDAL != null)
                {
                    oInsurerDAL = null;
                }
            }
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
    }
}

InsurerController.cs

    namespace InformationServices.API.Controllers
{
    [RoutePrefix("V1")]
    [ControllerExceptionFilter]
    public class InsurerController : ApiController
    {
    private IInsurerRepository InsurerRepository;

    private static ILog logger = log4net.LogManager.GetLogger(typeof(InsurerController));

    public InsurerController(IInsurerRepository repository)
    {
        InsurerRepository = repository;
        InsurerRepository.ConsumerDetails = CommonFunctions.FetchConsumerDataFromHeader();
    }


    [HttpGet]
    [HttpOptions]
    public async Task<IHttpActionResult> GetInsurer(string cover, string version, string srcKey)
    {
    //code here
}
}

}

我也在使用下面的代码将它注册到一个容器中

var container = new UnityContainer();
container.RegisterType<IInsurerDAL, InsurerDAL>(new HierarchicalLifetimeManager());
GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);

当我尝试使用此 Web API 时，我仍然遇到以下问题：

依赖关系解析失败，类型= \"InformationServices.API.Controllers.InsurerController\"，名称 = \"(none)\"。\r\n出现异常 while: 解析时。\r\n异常是： InvalidOperationException - 当前类型， InformationServices.Repository.IInsurerRepository，是一个接口和无法构建。您是否缺少类型映射？

【问题讨论】：

标签： asp.net asp.net-mvc asp.net-mvc-3 asp.net-mvc-4 asp.net-web-api

【解决方案1】：

您指向并解析到其他没有将您的接口注册到具体类的容器。你应该让它们成为同一个容器。

抽象步骤：

您创建并设置 UnityContainer 作为默认值DependencyResolver Container
您在容器内注册类型之间的映射。即 container.Register<IInsurerDAL, InsurerDal>
您通过传递所需的类型对象来使用Constructor Dependency Injection。即 InsurerRepository(IInsurerDAL insurerDal)
您根据自己的需要保存\使用已解析的对象。 - 不是强制性的。

实际代码更改：

打开你是 Global.asax 并添加

var container = new UnityContainer();
DependencyResolver.SetResolver(new UnityDependencyResolver(container));

在你的 InsurerRepository 构造函数中删除到以下几行：

var container = new UnityContainer();
oInsurerDAL = container.Resolve<InsurerDAL>();

并使用依赖注入原理将您的 InsurerRepository 构造函数更改为以下内容。

public InsurerRepository(IInsurerDAL insurerDal) {
    oInsurerDAL = insurerDal;

并将InsurerDAL oInsurerDAL; 字段更改为IInsurerDAL oInsurerDAL;

【讨论】：