asp.net-mvc – 如何使用启用了延迟加载的Automapper和EF4 DbCon

发布时间：2020-12-16 04:11:07 所属栏目：asp.Net 来源：网络整理

导读：我正在使用Automapper在Entity和ViewModel对象之间进行映射(在两个方向上).该模型使用EF4 DbContext POCO并需要启用LazyLoading(因此代理生成). 我在尝试从viewmodel更新现有实体时遇到了问题.当我调用Mapper.Map(vm,entity)时,Automapper会抛出异常.我的问

我正在使用Automapper在Entity和ViewModel对象之间进行映射(在两个方向上).该模型使用EF4 DbContext POCO并需要启用LazyLoading(因此代理生成).

我在尝试从viewmodel更新现有实体时遇到了问题.当我调用Mapper.Map(vm,entity)时,Automapper会抛出异常.我的问题是：你如何使用Automapper使用EF代理对象？

代码看起来(简化)像这样：

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)来更新现有的实体对象时,我得到了异常：

'Mapper.Map(viewModel,resultSet)' threw an exception of type 'AutoMapper.AutoMapperMappingException'
base {System.Exception}: {"Missing type map configuration or unsupported mapping.nnMapping types:rnResultSetView -> ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2rnSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView -> System.Data.Entity.DynamicProxies.ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2nnDestination path:nResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2nnSource 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.nnMapping types:rnResultSetView -> ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2rnSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView -> System.Data.Entity.DynamicProxies.ResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2nnDestination path:nResultSet_692D75838D4DC59B922F3E88CF1B10516CBF6CD8A32C4BE2F3FCC28CE83F0BD2nnSource value:nSciensus.Applications.ClinicalStudies.Web.Areas.Patient.Models.ResultSetView"
StackTrace: ""

解决方法

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

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

这个地方出现了问题：

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

所以没有问题的变化：

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

（编辑：李大同）

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