C# 反序列化JSON时如何将ObjectCreationHandling.Replace应用于选定属性？

我有一个类，它包含一个

List

属性，其默认构造函数分配列表并用一些默认值填充列表，例如：

public class Configuration
{
    public List<Tuple<int, int, int>> MyThreeTuple { get; set; }

    public Configuration()
    {
        MyThreeTuple = new List<Tuple<int, int, int>>();
        MyThreeTuple.Add(new Tuple<int, int, int>(-100, 20, 501));
        MyThreeTuple.Add(new Tuple<int, int, int>(100, 20, 864));
        MyThreeTuple.Add(new Tuple<int, int, int>(500, 20, 1286));
    }
}

---

如何应用

对象创建处理。有选择地替换对象图中的某些属性，而不是其他属性？
您有几种方法可以强制替换列表，而不是重复使用列表：

您可以向列表属性中添加，以指示应替换而不是重复使用该属性：

public class Configuration
{
    [JsonProperty(ObjectCreationHandling = ObjectCreationHandling.Replace)]
    public List<Tuple<int, int, int>> MyThreeTuple { get; set; }
}

然后将其与以下内容一起使用：


如果希望替换而不是重复使用所有列表属性，可以进行自定义，以执行以下操作：

public class ListReplacementContractResolver : DefaultContractResolver
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    static readonly ListReplacementContractResolver instance;

    // Using a static constructor enables fairly lazy initialization.  http://csharpindepth.com/Articles/General/Singleton.aspx
    static ListReplacementContractResolver() { instance = new ListReplacementContractResolver(); }

    public static ListReplacementContractResolver Instance { get { return instance; } }

    protected ListReplacementContractResolver() : base() { }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var jsonProperty = base.CreateProperty(member, memberSerialization);
        if (jsonProperty.ObjectCreationHandling == null && jsonProperty.PropertyType.GetListType() != null)
            jsonProperty.ObjectCreationHandling = ObjectCreationHandling.Replace;
        return jsonProperty;
    }
}

public static class TypeExtensions
{
    public static Type GetListType(this Type type)
    {
        while (type != null)
        {
            if (type.IsGenericType)
            {
                var genType = type.GetGenericTypeDefinition();
                if (genType == typeof(List<>))
                    return type.GetGenericArguments()[0];
            }
            type = type.BaseType;
        }
        return null;
    }
}


如果集合是get only（本例中不是），请参阅

您有几种替代方法可以强制替换列表，而不是重复使用：

您可以向列表属性中添加，以指示应替换而不是重复使用该属性：

public class Configuration
{
    [JsonProperty(ObjectCreationHandling = ObjectCreationHandling.Replace)]
    public List<Tuple<int, int, int>> MyThreeTuple { get; set; }
}

然后将其与以下内容一起使用：


如果希望替换而不是重复使用所有列表属性，可以进行自定义，以执行以下操作：

public class ListReplacementContractResolver : DefaultContractResolver
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    static readonly ListReplacementContractResolver instance;

    // Using a static constructor enables fairly lazy initialization.  http://csharpindepth.com/Articles/General/Singleton.aspx
    static ListReplacementContractResolver() { instance = new ListReplacementContractResolver(); }

    public static ListReplacementContractResolver Instance { get { return instance; } }

    protected ListReplacementContractResolver() : base() { }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var jsonProperty = base.CreateProperty(member, memberSerialization);
        if (jsonProperty.ObjectCreationHandling == null && jsonProperty.PropertyType.GetListType() != null)
            jsonProperty.ObjectCreationHandling = ObjectCreationHandling.Replace;
        return jsonProperty;
    }
}

public static class TypeExtensions
{
    public static Type GetListType(this Type type)
    {
        while (type != null)
        {
            if (type.IsGenericType)
            {
                var genType = type.GetGenericTypeDefinition();
                if (genType == typeof(List<>))
                    return type.GetGenericArguments()[0];
            }
            type = type.BaseType;
        }
        return null;
    }
}


如果集合是get only（本例中不是），请参阅

请发表你的问题，这将极大地帮助我们帮助你。dbc，这是我所见过的最漂亮的编辑。请发表你的问题，这将极大地帮助我们帮助你。dbc，这是我所见过的最漂亮的编辑。太棒了！谢谢@dbc，这正是我需要的。我的问题是System.Net.Mail.MailAddress，因此添加属性从来都不是一个选项。我选择了解决方案4，一个定制的合同解析程序。再次感谢！明亮的谢谢@dbc，这正是我需要的。我的问题是System.Net.Mail.MailAddress，因此添加属性从来都不是一个选项。我选择了解决方案4，一个定制的合同解析程序。再次感谢！
public class ConfigurationConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return typeof(Configuration).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var config = (existingValue as Configuration ?? (Configuration)serializer.ContractResolver.ResolveContract(objectType).DefaultCreator());
        if (config.MyThreeTuple != null)
            config.MyThreeTuple.Clear();
        serializer.Populate(reader, config);
        return config;
    }

    public override bool CanWrite { get { return false; } }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

var settings = new JsonSerializerSettings { Converters = new JsonConverter[] { new ConfigurationConverter() } };

public class ListReplacementContractResolver : DefaultContractResolver
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    static readonly ListReplacementContractResolver instance;

    // Using a static constructor enables fairly lazy initialization.  http://csharpindepth.com/Articles/General/Singleton.aspx
    static ListReplacementContractResolver() { instance = new ListReplacementContractResolver(); }

    public static ListReplacementContractResolver Instance { get { return instance; } }

    protected ListReplacementContractResolver() : base() { }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var jsonProperty = base.CreateProperty(member, memberSerialization);
        if (jsonProperty.ObjectCreationHandling == null && jsonProperty.PropertyType.GetListType() != null)
            jsonProperty.ObjectCreationHandling = ObjectCreationHandling.Replace;
        return jsonProperty;
    }
}

public static class TypeExtensions
{
    public static Type GetListType(this Type type)
    {
        while (type != null)
        {
            if (type.IsGenericType)
            {
                var genType = type.GetGenericTypeDefinition();
                if (genType == typeof(List<>))
                    return type.GetGenericArguments()[0];
            }
            type = type.BaseType;
        }
        return null;
    }
}

var settings = new JsonSerializerSettings { ContractResolver = ListReplacementContractResolver.Instance };