Question

以下映射代码会导致automapper在完成映射时抛出异常。

mapper.CreateMap<SqlDataReader, CodeModel>()
      .ForMember(dest => dest.Code, 
                 options => options.MapFrom(src => src["code"] != null ? 
                                                   src["code"].ToString() :
                                                   string.Empty));

这真的很奇怪，src["code"]有一个值，它是"E"，甚至在automapper消息中都说明了这一点。

有没有人对此问题或如何解决此问题有任何见解？

堆栈追踪：

[NullReferenceException：对象引用未设置为的实例   对象。] AutoMapper.Mappers.TypeMapMapper.Map（ResolutionContext   context，IMappingEngineRunner mapper）+116
  AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map（ResolutionContext   上下文）+459

[AutoMapperMappingException：

映射类型：字符串 - ＆gt; String System.String - ＆gt; System.String

目标路径：CodeModel.Code

来源价值：E]
  AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map（ResolutionContext   上下文）+537
  AutoMapper.Mappers.DataReaderMapper.MapPropertyValue（ResolutionContext   context，IMappingEngineRunner mapper，Object mappedObject，PropertyMap   propertyMap）+305
  AutoMapper.Mappers.DataReaderMapper.MapPropertyValues（ResolutionContext   context，IMappingEngineRunner mapper，Object result）+210
  AutoMapper.Mappers.DataReaderMapper.Map（ResolutionContext context，   IMappingEngineRunner mapper）+639
  AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map（ResolutionContext   上下文）+477 AutoMapper.MappingEngine.Map（对象源，类型   sourceType，Type destinationType，Action 1 opts) +176 AutoMapper.MappingEngine.Map(Object source, Action 1 opts）+162
  AutoMapper.MappingEngine.Map（对象源）+143

Answer 1

尝试使用ResolveUsing方法，而不是方法MapFrom，但在您的情况下，这两种方法都应该按预期工作。尝试查看是否存在任何配置问题。

  mapper.CreateMap<SqlDataReader, CodeModel>()
          .ForMember(dest => dest.Code, 
                     options => options.ResolveUsing(src => src["code"] != null ? 
                                                       src["code"].ToString() :
                                                       string.Empty));

我用SqlReaderMock创建了一个工作示例。我假设您的SqlReader执行上下文很好。

//Arrange
var configStore = new ConfigurationStore(new TypeMapFactory(), MapperRegistry.AllMappers());
configStore.CreateMap<SqlDataReaderMock, Destination>()
    .ForMember(dest => dest.Name, opt => opt.ResolveUsing(src => src["tyto"] != null
                                                                        ? src["tyto"].ToString()
                                                                        : String.Empty));
var _mappingEngine = new MappingEngine(configStore);

//Act
var result = _mappingEngine.Map<Destination>(new SqlDataReaderMock());

//Assert
Assert.AreEqual("otyt", result.Name);


class Destination
{
    public string Name { get; set; }
}


class SqlDataReaderMock
{
    public string this[string value]
    {
        get
        {
            return new string(value
                                    .ToCharArray()
                                    .Reverse()
                                    .ToArray());
        }
    }
}

自动映射例外

1 个答案: