SignalR Typenamehandling

我试图让SignalR与自定义JsonSerializerSettings一起使用它的有效负载，特别是我试图设置TypeNameHandling = TypeNameHandling.Auto 。

问题似乎是，SignalR使用hubConnection.JsonSerializer和hubConnection.JsonSerializer GlobalHost.DependencyResolver.Resolve()作为其内部数据结构，然后导致各种破坏（当我设置TypeNameHandling.All时内部服务器崩溃）作为最粗鲁的例子，但是使用TypeNameHandling.Auto我也会遇到问题，特别是当涉及IProgress回调时）。

是否有任何解决方法或我只是做错了？

用于演示的示例代码：

服务器：

 class Program { static void Main(string[] args) { using (WebApp.Start("http://localhost:8080")) { Console.ReadLine(); } } } public class Startup { public void Configuration(IAppBuilder app) { var hubConfig = new HubConfiguration() { EnableDetailedErrors = true }; GlobalHost.DependencyResolver.Register(typeof(JsonSerializer), ConverterSettings.GetSerializer); app.MapSignalR(hubConfig); } } public interface IFoo { string Val { get; set; } } public class Foo : IFoo { public string Val { get; set; } } public class MyHub : Hub { public IFoo Send() { return new Foo { Val = "Hello World" }; } } 

客户：

 class Program { static void Main(string[] args) { Task.Run(async () => await Start()).Wait(); } public static async Task Start() { var hubConnection = new HubConnection("http://localhost:8080"); hubConnection.JsonSerializer = ConverterSettings.GetSerializer(); var proxy = hubConnection.CreateHubProxy("MyHub"); await hubConnection.Start(); var result = await proxy.Invoke("Send"); Console.WriteLine(result.GetType()); } 

共享：

 public static class ConverterSettings { public static JsonSerializer GetSerializer() { return JsonSerializer.Create(new JsonSerializerSettings() { TypeNameHandling = TypeNameHandling.All }); } } 

Answer 1

这可以通过利用类型和SignalR类型在不同程序集中的事实来完成。 我们的想法是创建一个适用于程序 JsonConverter 所有类型的JsonConverter 。 当在对象图中首次遇到来自其中一个程序集的类型（可能作为根对象）时，转换器将临时设置jsonSerializer.TypeNameHandling = TypeNameHandling.Auto ，然后继续执行该类型的标准序列化，禁用其自身持续时间以防止无限递归：

 public class PolymorphicAssemblyRootConverter : 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; } } readonly HashSet assemblies; public PolymorphicAssemblyRootConverter(IEnumerable assemblies) { if (assemblies == null) throw new ArgumentNullException(); this.assemblies = new HashSet(assemblies); } public override bool CanConvert(Type objectType) { return assemblies.Contains(objectType.Assembly); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { using (new PushValue(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters using (new PushValue(TypeNameHandling.Auto, () => serializer.TypeNameHandling, val => serializer.TypeNameHandling = val)) { return serializer.Deserialize(reader, objectType); } } public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { using (new PushValue(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters using (new PushValue(TypeNameHandling.Auto, () => 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 : IDisposable { Action setValue; T oldValue; public PushValue(T value, Func getValue, Action 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 } 

然后在启动时，您将此转换器添加到默认的JsonSerializer ，传入要为其应用"$type"的程序集。

更新

如果由于某种原因在启动时传递程序集列表不方便，您可以通过objectType.Namespace启用转换器。 生活在指定命名空间中的所有类型都将自动使用TypeNameHandling.Auto序列化。

或者，您可以引入一个以组件，类或接口为目标的Attribute ，并在与适当的转换器结合使用时启用TypeNameHandling.Auto ：

 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().Any()) return true; if (objectType.GetCustomAttributes(true).Any()) return true; foreach (var type in objectType.GetInterfaces()) if (type.GetCustomAttributes(true).Any()) return true; return false; } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { using (new PushValue(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters using (new PushValue(TypeNameHandling.Auto, () => serializer.TypeNameHandling, val => serializer.TypeNameHandling = val)) { return serializer.Deserialize(reader, objectType); } } public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { using (new PushValue(true, () => Disabled, val => Disabled = val)) // Prevent infinite recursion of converters using (new PushValue(TypeNameHandling.Auto, () => 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)); } } } [System.AttributeUsage(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Interface)] public class EnableJsonTypeNameHandlingAttribute : System.Attribute { public EnableJsonTypeNameHandlingAttribute() { } } 

注意 – 测试了各种测试用例但不测试SignalR本身，因为我目前没有安装它。

TypeNameHandling注意

使用TypeNameHandling ，请注意Newtonsoft文档中的这一注意事项：

当您的应用程序从外部源反序列化JSON时，应谨慎使用TypeNameHandling。 使用非None以外的值进行反序列化时，应使用自定义SerializationBindervalidation传入类型。

有关可能需要这样做的讨论，请参阅Newtonsoft Json中的TypeNameHandling警告 。

Answer 2

我知道这是一个相当陈旧的线程，并且有一个公认的答案。

但是，我遇到的问题是我无法使服务器正确读取收到的json，也就是说它只读取了基类

但是，问题的解决方案非常简单：

我在参数类之前添加了这一行：

 [JsonConverter(typeof(PolymorphicAssemblyRootConverter), typeof(ABase))] public class ABase { } public class ADerived : ABase { public AInner[] DifferentObjects { get; set;} } public class AInner { } public class AInnerDerived : AInner { } ... public class PolymorphicAssemblyRootConverter: JsonConverter { public PolymorphicAssemblyRootConverter(Type classType) : this(new Assembly[]{classType.Assembly}) { } // Here comes the rest of PolymorphicAssemblyRootConverter } 

无需在客户端的代理连接上设置JsonSerializer并将其添加到GlobalHost.DependencyResolver。

我花了很长时间才弄明白，我在客户端和服务器上使用SignalR 2.2.1。