Automapper地图物业

Question

迁移后V2.0我抓住这个问题

我尝试这样的映射属性：当我使用映射

public class SurveyFormView 
{ 
    public MultiSelectList Statistics { get; set; } 
} 
public class SurveyForm 
{ 

    ICollection<Statistic> statistics = new List<Statistic>(); 
    public virtual ICollection<Statistic> Statistics 
    { 
     get { return statistics; } 
     set { statistics = value; } 
    } 
} 


Mapper.CreateMap<SurveyForm, SurveyFormView>(). 
      ForMember(x => x.Statistics, 
         m => 
         m.MapFrom(x => new MultiSelectList(x.Statistics))). 

：model = Mapper.Map<SurveyForm, SurveyFormView>(item); 我得到：

[ArgumentException: Type 'System.Web.Mvc.MultiSelectList' does not have a default constructor] 
    System.Linq.Expressions.Expression.New(Type type) +2741878 
    AutoMapper.<>c__DisplayClass1.<CreateCtor>b__0(Type t) in c:\dev\AutoMapper\src\AutoMapper\Internal\DelegateFactory.cs:142 
    System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory) +72 
    AutoMapper.DelegateFactory.CreateCtor(Type type) in c:\dev\AutoMapper\src\AutoMapper\Internal\DelegateFactory.cs:140 
    AutoMapper.Mappers.ObjectCreator.CreateObject(Type type) in c:\dev\AutoMapper\src\AutoMapper\Mappers\ObjectCreator.cs:47 
    AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.CreateObject(ResolutionContext context) in c:\dev\AutoMapper\src\AutoMapper\MappingEngine.cs:362 
    AutoMapper.Mappers.EnumerableMapperBase`1.CreateDestinationObject(ResolutionContext context, Type destinationElementType, Int32 count, IMappingEngineRunner mapper) in c:\dev\AutoMapper\src\AutoMapper\Mappers\EnumerableMapperBase.cs:64 
    AutoMapper.Mappers.EnumerableMapperBase`1.Map(ResolutionContext context, IMappingEngineRunner mapper) in c:\dev\AutoMapper\src\AutoMapper\Mappers\EnumerableMapperBase.cs:21 
    AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) in c:\dev\AutoMapper\src\AutoMapper\MappingEngine.cs:303 

Answer 1

当您需要映射到无参数构造函数的目标类型时，您需要使用ConstructUsing而不是MapFrom：

Mapper.CreateMap<ICollection<Statistic>, MultiSelectList>() 
    .ConstructUsing(c => new MultiSelectList(c)); 
Mapper.CreateMap<SurveyForm, SurveyFormView>(); 

如果你注册的源集合为IEnumerable它也将工作：

Mapper.CreateMap<IEnumerable, MultiSelectList>() 
    .ConstructUsing(c => new MultiSelectList(c));