Question

我正在使用此线程答案中的转换器（更新版本）：SignalR Typenamehandling

public class EnableJsonTypeNameHandlingConverter : JsonConverter
{

    [ThreadStatic]
    static bool disabled;

    // Disables the converter in a thread-safe manner.
    bool Disabled { get { return disabled; } set { disabled = value; } }

    public override bool CanWrite { get { return !Disabled; } }

    public override bool CanRead { get { return !Disabled; } }

    public override bool CanConvert(Type objectType)
    {
        if (Disabled)
            return false;
        if (objectType.Assembly.GetCustomAttributes<EnableJsonTypeNameHandlingAttribute>().Any())
            return true;
        if (objectType.GetCustomAttributes<EnableJsonTypeNameHandlingAttribute>(true).Any())
            return true;
        foreach (var type in objectType.GetInterfaces())
            if (type.GetCustomAttributes<EnableJsonTypeNameHandlingAttribute>(true).Any())
                return true;
        return false;
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        using (new PushValue<bool>(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters
        using (new PushValue<TypeNameHandling>(TypeNameHandling.All, () => serializer.TypeNameHandling, val => serializer.TypeNameHandling = val))
        {
            return serializer.Deserialize(reader, objectType);
        }
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        using (new PushValue<bool>(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters
        using (new PushValue<TypeNameHandling>(TypeNameHandling.All, () => serializer.TypeNameHandling, val => serializer.TypeNameHandling = val))
        {
            // Force the $type to be written unconditionally by passing typeof(object) as the type being serialized.
            serializer.Serialize(writer, value, typeof(object));
        }
    }
}

public struct PushValue<T> : IDisposable
{
    Action<T> setValue;
    T oldValue;

    public PushValue(T value, Func<T> getValue, Action<T> setValue)
    {
        if (getValue == null || setValue == null)
            throw new ArgumentNullException();
        this.setValue = setValue;
        this.oldValue = getValue();
        setValue(value);
    }

    #region IDisposable Members

    // By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.
    public void Dispose()
    {
        if (setValue != null)
            setValue(oldValue);
    }

    #endregion
}

[System.AttributeUsage(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Interface)]
public class EnableJsonTypeNameHandlingAttribute : System.Attribute
{
    public EnableJsonTypeNameHandlingAttribute()
    {
    }
}

这是我添加转换器的方式：

    _hubConnection = new HubConnection(url);
    var converter = new EnableJsonTypeNameHandlingConverter();
    _hubConnection.JsonSerializer.Converters.Add(converter);

和

    var serializer = GlobalHost.DependencyResolver.GetService(typeof(JsonSerializer)) as JsonSerializer;
    var converter = new EnableJsonTypeNameHandlingConverter();
    serializer.Converters.Add(converter);
    GlobalHost.DependencyResolver.Register(typeof(JsonSerializer), () => serializer);

我在转换器的ReadJson和WriteJson中设置了断点。我只打了WriteJson断点。永远不会从转换器执行ReadJson。我发送派生类作为基类，我无法将其强制转换为派生类。

信号R自定义转换器不读取

0 个答案: