Csharp 为什么在使用JsonDerivedType序列化泛型时缺少$type

发布于12月04日

以下是我的代码:

public partial class MainWindow : Window
{        
    public MainWindow()
    {
        InitializeComponent();
        Debug.WriteLine(JsonSerializer.Serialize<TestModel>(new TestModel() { Name = "123", Time = DateTime.Now }));
        Debug.WriteLine(JsonSerializer.Serialize<TestModelWithGeneric<int>>(new TestModelWithGeneric<int>() { Name = "123", Time = DateTime.Now ,Value=1}));
        Debug.WriteLine(JsonSerializer.Serialize<TestModelWithGeneric<string>>(new TestModelWithGeneric<string>() { Name = "123", Time = DateTime.Now, Value = "123" }));
    }
    [JsonDerivedType(typeof(TestModel), typeDiscriminator: "Base")]
    [JsonDerivedType(typeof(TestModelWithGeneric<int>), typeDiscriminator: "TestModelWithInt")]
    [JsonDerivedType(typeof(TestModelWithGeneric<string>), typeDiscriminator: "TestModelWithString")]
    public class TestModel {
        public string Name{ get; set; }
        public DateTime Time { get; set; }
    }
    public class TestModelWithGeneric<T> :TestModel{ 
        public T Value { get; set; }
    }
}

输出为:

{"$type":"Base","Name":"123","Time":"2023-12-04T15:29:49.7867248+08:00"}
{"Value":1,"Name":"123","Time":"2023-12-04T15:29:49.8314012+08:00"}
{"Value":"123","Name":"123","Time":"2023-12-04T15:29:49.8354174+08:00"}

正如您所看到的，当存在泛型类型时，它总是缺少JsonDerivedType不起作用的$type.

我的代码有什么问题？

我使用的框架是.Net8.

Console.WriteLine(JsonSerializer.Serialize<TestModel>(new TestModel() { Name = "123", Time = DateTime.Now })); Console.WriteLine(JsonSerializer.Serialize<TestModel>(new TestModelWithGeneric<int>() { Name = "123", Time = DateTime.Now ,Value=1})); Console.WriteLine(JsonSerializer.Serialize<TestModel>(new TestModelWithGeneric<string>() { Name = "123", Time = DateTime.Now, Value = "123" }));

public class JsonHierarchyTypeInfoResolver : DefaultJsonTypeInfoResolver { public override JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options) { var result = base.GetTypeInfo(type, options); if (type != typeof(TestModel) && type.IsAssignableTo(typeof(TestModel))) { var baseInfo = base.GetTypeInfo(typeof(TestModel), options); foreach (var derivedType in baseInfo.PolymorphismOptions.DerivedTypes) { if (derivedType.DerivedType.IsAssignableTo(type)) { result.PolymorphismOptions ??= new JsonPolymorphismOptions(); result.PolymorphismOptions.DerivedTypes.Add(derivedType); } } } return result; } }

var options = new JsonSerializerOptions { TypeInfoResolver = new JsonHierarchyTypeInfoResolver() }; Console.WriteLine(JsonSerializer.Serialize( new TestModel { Name = "123", Time = DateTime.Now } , options)); Console.WriteLine(JsonSerializer.Serialize( new TestModelWithGeneric<int> { Name = "123", Time = DateTime.Now ,Value=1} , options)); Console.WriteLine(JsonSerializer.Serialize( new TestModelWithGeneric<string> { Name = "123", Time = DateTime.Now, Value = "123" } , options));

{"$type":"Base","Name":"123","Time":"2023-12-04T12:37:43.9072465+03:00"} {"$type":"TestModelWithInt","Value":1,"Name":"123","Time":"2023-12-04T12:37:44.1239771+03:00"} {"$type":"TestModelWithString","Value":"123","Name":"123","Time":"2023-12-04T12:37:44.1282147+03:00"}

Csharp 为什么在使用JsonDerivedType序列化泛型时缺少$type

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