AutoMapper與Json.NET JObject對應問題

使用套件:
Json.NET 7.0.1 : https://www.nuget.org/packages/Newtonsoft.Json/7.0.1
AutoMapper 4.04 : https://www.nuget.org/packages/AutoMapper/4.0.4

今天碰到一個問題，就是有個API回傳值的欄位是不固定無法掌握的，所以只好在轉型成強型別時以object當做該屬性的類別，但JsonConvert碰到類別為Object的東西就會轉成JObject ,而AutoMapper對應JObject會炸掉。以下是簡單時間的範例Code

void Main()
{
 Mapper.CreateMap<source, destination>()
 .ForMember(d => d.d_name, o => o.MapFrom(s => s.name))
 .ForMember(d => d.d_obj, o => o.MapFrom(s => s.obj));

 source test = new source 
 {
  name = "test",
  obj = new {code = 100},
 };

 var result = Mapper.Map<destination>(test);
 result.Dump();
}

public class source
{
 public string name { get; set; }
 public object obj { get; set; }
}

public class destination
{
 public string d_name { get; set; }
 public object d_obj { get; set; }
}

Source與Destination都有個property為object的類別屬性，在Main()裡面也想好兩個類別的對應關係，並且先準備好Source 然後透過AutoMapper轉出Result,在以上的範例執行正確沒問題

換個寫法

void Main()
{
 Mapper.CreateMap<source, destination>()
 .ForMember(d => d.d_name, o => o.MapFrom(s => s.name))
 .ForMember(d => d.d_obj, o => o.MapFrom(s => s.obj));

 source test = JsonConvert.DeserializeObject<source>("{\"name\":\"test\",\"obj\" : {\"code\":100}}");
 var result = Mapper.Map<destination>(test);
 result.Dump();
}

public class source
{
 public string name { get; set; }
 public object obj { get; set; }
}

public class destination
{
 public string d_name { get; set; }
 public object d_obj { get; set; }
}

差別只在於原本Source改成透過Json.Net由字串轉回來而已，這時候只要執行到AutoMapper那一行就會爆炸，錯誤訊息如下

AutoMapperMappingException:

Mapping types:
JObject -> JObject
Newtonsoft.Json.Linq.JObject -> Newtonsoft.Json.Linq.JObject

Destination path:
destination.d_obj.d_obj

Source value:
{
“code”: 100
}

JsonConvert碰到目標為Object型別的欄位，會轉成JObject塞進去，AutoMapper用它來對應，
所以如果要解決這個問題需要做一些處理

//將Mapper改成如下
 Mapper.CreateMap<source, destination>()
 .ForMember(d => d.d_name, o => o.MapFrom(s => s.name))
 .ForMember(d => d.d_obj, o => o.ResolveUsing(s =>
 {
  if (s.obj is JObject)
  {
   var temp = s.obj as JObject;
   return temp.ToObject<Dictionary<string, object>>();
  }
  return s.obj;
 }));

這樣就可以正確地取出了