自动映射器自定义解析程序引发空异常
本文关键字:程序 异常 映射 自定义 | 更新日期: 2023-09-27 18:32:43
所以我有一个运行良好的移动服务,并希望添加DTO的符号。我使用 AutoMapper 在我的模型和 DTO 模型之间进行映射,但数据库的复杂性和我想要的结果迫使我使用自定义解析器,这反过来又会引发空异常。
具体来说 - 映射器初始化
Mapper.Initialize(cfg =>
{
cfg.CreateMap<Contact, MobileContact>()
.ForMember(mobcont => mobcont.Favorite, map => map.ResolveUsing<ContactResolver>());//.UseValue(true));//
cfg.CreateMap<MobileContact, Contact>();
});
我的自定义解析器是
public class ContactResolver : ValueResolver<Contact, bool>
{
protected override bool ResolveCore(Contact a)
{
return true;
}
}
编辑:最喜欢的当然是布尔值
如果我不使用自定义解析程序并使用 .使用值(真(它工作得很好
尽管如上所示使用自定义解析程序的常见 get 请求会引发以下异常:
Exception=System.NullReferenceException: Object reference not set to an instance of an object.
at AutoMapper.QueryableExtensions.Extensions.ResolveExpression(PropertyMap propertyMap, Type currentType, Expression instanceParameter)
at AutoMapper.QueryableExtensions.Extensions.CreateMemberBindings(IMappingEngine mappingEngine, TypePair typePair, TypeMap typeMap, Expression instanceParameter, IDictionary`2 typePairCount)
at AutoMapper.QueryableExtensions.Extensions.CreateMapExpression(IMappingEngine mappingEngine, TypePair typePair, Expression instanceParameter, IDictionary`2 typePairCount)
at AutoMapper.QueryableExtensions.Extensions.CreateMapExpression(IMappingEngine mappingEngine, TypePair typePair, IDictionary`2 typePairCount)
at AutoMapper.QueryableExtensions.Extensions.<>c__DisplayClass1`2.<CreateMapExpression>b__0(TypePair tp)
at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
at AutoMapper.Internal.DictionaryFactoryOverride.ConcurrentDictionaryImpl`2.GetOrAdd(TKey key, Func`2 valueFactory)
at AutoMapper.QueryableExtensions.Extensions.CreateMapExpression[TSource,TDestination](IMappingEngine mappingEngine)
at AutoMapper.QueryableExtensions.ProjectionExpression`1.To[TResult]()
at Microsoft.WindowsAzure.Mobile.Service.MappedEntityDomainManager`2.Query()
at azmobtestService.Models.MobileContactDomainManager.Query() in c:'Users'n.atlas'Source'Repos'JPhoneBook'Service'azmobtestService'Models'MobileContactDomainManager.cs:line 104
at Microsoft.WindowsAzure.Mobile.Service.TableController`1.Query(), Id=75849f58-ccb0-4a6b-8a77-491f13fcb717, Category='App.Controllers.Tables'
如果您所做的只是在所有情况下都将 favorite 解析为 true(这是不对的,但这是您提供的代码,所以我会使用它(,那么您的映射器可能只是.ForMember(mobcont => mobcont.Favorite, expression => expression.MapFrom(source => true));
如果您正在寻找普通的价值解析器,我会选择这样的 ITypeConverter:
public class ContactToMobileContactTypeConverter : ITypeConverter<Contact, MobileContact>
{
public MobileContact Convert(ResolutionContext context)
{
var contact = (Contact)context.SourceValue;
var mobileContact = new MobileContact();
if(contact != null) {
//database query
//assign values
}
return mobileContact;
}
}