仅适用于 Json.NET 中的一个属性的自定义序列化器，无需更改模型类

我需要执行如下操作，但我需要在不添加属性或以其他方式污染模型类的情况下执行此操作。理想的解决方案是通过JsonSerializerSettings，不干扰其他自定义序列化。顺便说一句，以下内容来自这个问题：JSON.NET 中特定对象的自定义转换 https://stackoverflow.com/questions/6404881/custom-conversion-of-specific-objects-in-json-net?rq=1

public class Person
{
    public string FirstName { get; set; }
    [JsonConverter(typeof(AllCapsConverter))]
    public string LastName { get; set; }
    // more properties here in the real example, some of which nest to properties that use their own JsonConverters.
}

The JsonConverter对于这个玩具示例（内容并不真正相关；相关的是我将其用于属性）：

public class AllCapsConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
        => objectType == typeof(string);

    public override bool CanRead => false;

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotSupportedException();
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var str = value as string;
        var upper = str.ToUpperInvariant();
        JToken j = JToken.FromObject(upper);
        j.WriteTo(writer);
    }
}

通过单元测试：

public class PersonSerializationTest
{
    [Fact]
    public void SerializePerson_LastNameCaps()
    {
        var person = new Person
        {
            FirstName = "George",
            LastName = "Washington"
        };
        var serialized = JsonConvert.SerializeObject(person);
        var expected = @"{""FirstName"":""George"",""LastName"":""WASHINGTON""}";
        Assert.Equal(expected, serialized);
    }
}

您可以通过编程方式应用JsonConverter模型类中的一个或多个属性，无需通过自定义使用属性ContractResolver。这是一个简单的示例，它适用于您的AllCapsConverter to the LastName您的财产Person班级。 （如果您正在寻找更强大的解决方案，请查看@dbc的answer https://stackoverflow.com/a/53768445/10263。我在这里的目的是展示一个可能有效的最简单的例子。）

public class CustomResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty prop = base.CreateProperty(member, memberSerialization);
        if (prop.DeclaringType == typeof(Person) && prop.UnderlyingName == "LastName")
        {
            prop.Converter = new AllCapsConverter();
        }
        return prop;
    }
}

这是更新的测试和Person显示如何使用解析器的模型：

public class PersonSerializationTest
{
    [Fact]
    public void SerializePerson_LastNameCaps()
    {
        var person = new Person
        {
            FirstName = "George",
            LastName = "Washington"
        };
        var settings = new JsonSerializerSettings
        {
            ContractResolver = new CustomResolver()
        };
        var serialized = JsonConvert.SerializeObject(person, settings);
        var expected = @"{""FirstName"":""George"",""LastName"":""WASHINGTON""}";
        Assert.Equal(expected, serialized);
    }
}

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

工作演示：https://dotnetfiddle.net/o4e3WP https://dotnetfiddle.net/o4e3WP