关于 c#:Can’t cast objects from Dictionary after using json.net deserialization

Can't cast objects from Dictionary after using json.net deserialization

我对反序列化字典有疑问。我无法将 Dictionary 中的对象转换为我的类型 Remiza...我正在使用 Json.net，我可以看到 Dictionary 中的对象是 JObject 而不是 Object，我不能将它们转换为我的类型。这是我的序列化/反序列化代码：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

private static Dictionary<Type, List<Object>> _ekstensje = new Dictionary<Type, List<Object>>();

public static void SerializeDictionary()
{
string json = JsonConvert.SerializeObject(_ekstensje);
System.IO.StreamWriter file = new System.IO.StreamWriter(@"c:\\tmp\\dictionary.json");
file.WriteLine(json);

file.Close();
}

public static void DeserializeDictionary()
{
string json;
System.IO.StreamReader file = new System.IO.StreamReader(@"c:\\tmp\\dictionary.json");
json = file.ReadToEnd();

file.Close();
_ekstensje = JsonConvert.DeserializeObject<Dictionary<Type, List<Object>>>(json);//Deserializacja Dictionary
Debug.WriteLine(_ekstensje);
}

public static List<Object> GetEkstensja(Type className)
{
List<Object> list = _ekstensje[className];
return list;
}

执行：

1
2
3
4
5
6
7

ObjectPlus.DeserializeDictionary();
List<Object> list = ObjectPlus.GetEkstensja(typeof(Remiza));
foreach (Object o in list)
{
Remiza r = (Remiza) o;
listaRemiz.Add(r);
}

我的问题是在投射到"Remiza"时出现异常：

1	An exception of type 'System.InvalidCastException' occurred in Osek_MAS_WPF.exe but was not handled in user code. Additional information: Unable to cast object of type 'Newtonsoft.Json.Linq.JObject' to type 'Osek_MAS_WPF.Remiza'.

感谢您的帮助！

相关讨论

为了使用 Json.NET 成功序列化和反序列化多态类型，您需要设置 TypeNameHandling = TypeNameHandling.Auto，如下所示：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62

public class ObjectPlus
{
// Replace with whatever file name is appropriate. My computer doesn't have a"c:\\tmp" directory.
static string JsonFileName { get { return Path.Combine(Path.GetTempPath(),"dictionary.json"); } }

static JsonSerializerSettings JsonSettings { get { return new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.Auto, Formatting = Formatting.Indented }; } }

private static Dictionary<Type, List<Object>> _ekstensje = new Dictionary<Type, List<Object>>();

public static void SerializeDictionary()
{
var path = JsonFileName;

using (var stream = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.Read))
using (var writer = new StreamWriter(stream))
{
var serializer = JsonSerializer.CreateDefault(JsonSettings);
serializer.Serialize(writer, _ekstensje);
}
}

public static void DeserializeDictionary()
{
var path = JsonFileName;
try
{
using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
using (var reader = new StreamReader(stream))
using (var jsonReader = new JsonTextReader(reader))
{
var serializer = JsonSerializer.CreateDefault(JsonSettings);
_ekstensje = serializer.Deserialize<Dictionary<Type, List<Object>>>(jsonReader);
}
}
catch (FileNotFoundException)
{
// File was not created yet, dictionary should be empty.
_ekstensje.Clear();
}
}

public static List<Object> GetEkstensja(Type className)
{
List<Object> list = _ekstensje[className];
return list;
}

public static void AddEkstensja< T >(T obj)
{
List<Object> list;
if (!_ekstensje.TryGetValue(obj.GetType(), out list))
list = _ekstensje[obj.GetType()] = new List<object>();
list.Add(obj);
}

internal static string ShowJsonContents()
{
if (!File.Exists(JsonFileName))
return string.Empty;
return File.ReadAllText(JsonFileName);
}
}

您现在应该能够在字典包含 Remiza.

的实例时对其进行序列化和反序列化

这适用于序列化为对象或集合的类型。但是，如果您的字典包含序列化为 JSON 原语的类型 - 例如 enum 或 long - 您可能需要将它们封装在类型package器中，沿着 Deserialize specific enum into system.enum in Json .Net.

(顺便说一句，您的 _ekstensje 字典不是线程安全的。)