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:

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    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:

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        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:

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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!


这应该允许您将 JObect 转换为您的 Remiza 类型。

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

我从下面链接的 stackoverflow 答案中得到了这个。如果我放的东西不起作用,请查看链接,它应该可以帮助您运行它。

https://stackoverflow.com/a/10221594/634769


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:

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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 enumlong – 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。)


原创文章,作者:ItWorker,如若转载,请注明出处:https://blog.ytso.com/269528.html

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