如何使用启用了延迟加载的 Automapper 和 EF4 DbContext 从 ViewModel 更新现有实体

我正在使用 Automapper 在 Entity 和 ViewModel 对象之间进行映射（双向）。该模型使用 EF4 DbContext POCO，并且需要启用 LazyLoading（因此需要启用代理生成）。

我在尝试从视图模型更新现有实体时遇到了问题。当我调用 Mapper.Map(vm,entity) 时，Automapper 抛出异常。我的问题是：您应该如何使用 Automapper 来处理 EF 代理对象？

代码看起来（简化）如下：

public class MyEntity
{
    public int Id {get;set;}
    public int Name {get;set;}
}

public class ViewModel
{
    public int Id {get;set;}
    public int Name {get;set;}
}

Mapper.CreateMap<MyEntity, ViewModel>();
Mapper.CreateMap<ViewModel, MyEntity>();

public ActionResult Edit(ViewModel vm)
{
    MyEntity entity = db.MyEntities.Find(vm.Id);
    Mapper.Map(vm, entity);
    db.Entry(entity).State = EntityState.Modified;
    db.SaveChanges();
}

当我调用 Mapper.Map(vm,entity) 来更新现有实体对象时，出现异常：

'Mapper.Map(viewModel, resultSet)' threw an exception of type 'AutoMapper.AutoMapperMappingException'
base {System.Exception}: {"Missing type map configuration or unsupported mapping.\n\nMapping types:\r\nResultSetView -> ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\r\nSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView -> System.Data.Entity.DynamicProxies.ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\n\nDestination path:\nResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\n\nSource value:\nSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView"}
Context: {Trying to map ResultSetView to ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2.}
Message: "Missing type map configuration or unsupported mapping.\n\nMapping types:\r\nResultSetView -> ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\r\nSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView -> System.Data.Entity.DynamicProxies.ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\n\nDestination path:\nResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2\n\nSource value:\nSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView"
StackTrace: ""

我查看了AutoMapper源代码：

    public TDestination Map<TSource, TDestination>(TSource source, TDestination destination)
    {
        return Map(source, destination, opts => { });
    }

    public TDestination Map<TSource, TDestination>(TSource source, TDestination destination, Action<IMappingOperationOptions> opts)
    {
        Type modelType = typeof(TSource);
        Type destinationType = (Equals(destination, default(TDestination)) ? typeof(TDestination) : destination.GetType());

        return (TDestination)Map(source, destination, modelType, destinationType, opts);
    }

这个地方出现了问题：

  Type destinationType = (Equals(destination, default(TDestination)) ? typeof(TDestination) : destination.GetType());

所以改一下就没有问题了：

  Mapper.Map(vm, entity,typeof(ViewModel),typeof(MyEntity));