反序列化期间的 JSON.Net Ignore Property

Question

我的班级设置如下：

public class Foo
{
    public string string1 { get; set; }
    public string string2 { get; set; }
    public string string3 { get; set; }
}

我正在使用 Json.Net 反序列化以下 Json 响应：

[
    {
        "number1": 1,
        "number2": 12345678901234567890,
        "number3": 3
    },
    {
        "number1": 9,
        "number2": 12345678901234567890,
        "number3": 8
    }
]

反序列化代码：

string json = @"[
    {
        ""number1"": 1,
        ""number2"": 12345678901234567890,
        ""number3"": 3
    },
    {
        ""number1"": 9,
        ""number2"": 12345678901234567890,
        ""number3"": 8
    }
]"

List<Foo> foos = JsonConvert.DeserializeObject<List<Foo>>(json);

number2 中的值超过了Int64，但我并不真正关心检索该值。有没有办法将number2 属性转换为字符串，或者在反序列化过程中完全忽略它？

我尝试将[JsonConverter(typeof(string))] 属性添加到string2 属性，但收到错误：Error creating System.String。我也试过设置typeof(decimal)。

我也尝试过使用[JsonIgnore]，但这不起作用。

Answer 1

您可以使用JsonSerializerSettings 对象的MissingMemberHandling 属性。

示例用法：

var jsonSerializerSettings = new JsonSerializerSettings();
jsonSerializerSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

JsonConvert.DeserializeObject<YourClass>(jsonResponse, jsonSerializerSettings);

更多信息here。

Answer 2

这是一个蹩脚的解决方法，但您可以创建一种手动加载 json 的方法。如果在没有自动反序列化器的情况下加载的数据太多，只需删除您不想要的节点。不过这要慢很多。

public static List<Foo> FromJson(string input) {
    var json = JToken.Parse(input);
    json["key"].Remove();
    var foo = JsonConvert.DeserializeObject<List<Foo>>(json.ToString());

}

这是一个有趣的问题，我想知道是否有人有更好的解决方案。

Answer 3

这是 Newtonsoft Json 首选的方式来忽略一个属性，而不必修改基于 http://james.newtonking.com/json/help/index.html?topic=html/ReducingSerializedJSONSize.htm 的类

这个用来忽略EF或者Linq2Sql的惰性引用属性

public class DynamicContractResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, 
        MemberSerialization memberSerialization)
    {
        Func<Type,bool> includeProperty = t => t.IsValueType || t.Namespace.StartsWith("System") && t.Namespace.StartsWith("System.Data")==false; 
        IList<JsonProperty> properties = base.CreateProperties(type, memberSerialization);
        var allProperties = properties.Select (p => new{p.PropertyName,Including=includeProperty(p.PropertyType), p.PropertyType});//.Dump("props");
        var warnProperties=allProperties.Where (a =>a.Including && a.PropertyType.IsValueType==false && a.PropertyType.Name.IsIgnoreCaseMatch("String")==false) ;

        //linq pad debugging helper
        //var propertyTypesSerializing= allProperties.Where (p => p.Including).Select (p => p.PropertyType).Distinct().OrderBy (p => p.Name).Dump();

        if(warnProperties.Any())
        {
            //LinqPad helper
            //Util.Highlight(warnProperties.ToArray()).Dump("warning flag raised, aborting");
            throw new ArgumentOutOfRangeException();
        }

        properties = properties.Where(p =>includeProperty(p.PropertyType)).ToList();
        return properties;
    }
}

所有.Dump() 调用只是linqpad 调试助手，不需要方法调用。

示例用法：

var inactives = from am in Aspnet_Memberships
        join mm in Member_members on am.UserId equals mm.Member_guid
        where mm.Is_active==false && mm.Org_id==1
        select new{am,mm};
        //inactives.Take(4).ToArray().Dump();
        var serialized = JsonConvert.SerializeObject(
            inactives.Skip(1).Select(i => i.mm).First(), 
            new  JsonSerializerSettings()
            {
                ContractResolver = new DynamicContractResolver(), 
                PreserveReferencesHandling = PreserveReferencesHandling.None,
                ReferenceLoopHandling= ReferenceLoopHandling.Ignore
            }); 
            //.Dump();

Answer 4

类似于@Maslow's solution，可以使用another general purpose "ignorer"：

var jsonResolver = new IgnorableSerializerContractResolver();
// ignore your specific property
jsonResolver.Ignore(typeof(Foo), "string2");
// ignore single datatype
jsonResolver.Ignore(typeof(System.Data.Objects.DataClasses.EntityObject));
var jsonSettings = new JsonSerializerSettings() { ReferenceLoopHandling = ReferenceLoopHandling.Ignore, ContractResolver = jsonResolver };

Answer 5

添加到 drzaus 答案： 您可以使用他建议的DefaultContractResolver .. 只是在其CreateProperty 中使用property.Ignored = true; 而不是property.ShouldSerialize，然后将JsonSerializerSettings 传递给DeserializeObject 函数或SerializeObject 函数时它都很好.

Answer 6

另类；

如果 ResponseAttribute 有模型或字符串参数

public class ResponseAttribute : Attribute { }

public class ModelItem
{
    [Response]
    public Guid Id { get; set; }
}

代码；

public class CustomJsonSerializer : JsonSerializerSettings
{
    public CustomJsonSerializer()
    {
        ContractResolver = new CustomContractResolver();
    }

    public CustomJsonSerializer(params string[] members)
    {
        ContractResolver = new CustomContractResolver(members);
    }

    public class CustomContractResolver : DefaultContractResolver
    {
        public string[] Members { get; set; }
        public CustomContractResolver(params string[] _members)
        {
            Members = _members;
        }

        protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
        {
            JsonProperty property = base.CreateProperty(member, memberSerialization);

            if (Members?.Length > 0)
                property.ShouldSerialize = instance => { return Members.Contains(member.Name); };
            else
                property.ShouldSerialize = instance => { return member.GetCustomAttribute<ResponseAttribute>() != null; };

            return property;
        }
    }
}

使用；

return new JsonResult(model, new CustomJsonSerializer());

或

return new JsonResult(model, new CustomJsonSerializer("Id","Test","Test2"));

Answer 7

这段代码对我来说就像一个魅力：

using System.Reflection;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
public class PropertyRenameAndIgnoreSerializerContractResolver : DefaultContractResolver
{
    private readonly Dictionary<Type, HashSet<string>> _ignores;
    private readonly Dictionary<Type, Dictionary<string, string>> _renames;

    public PropertyRenameAndIgnoreSerializerContractResolver()
    {
        _ignores = new Dictionary<Type, HashSet<string>>();
        _renames = new Dictionary<Type, Dictionary<string, string>>();
    }

    public void IgnoreProperty(Type type, params string[] jsonPropertyNames)
    {
        if (!_ignores.ContainsKey(type))
            _ignores[type] = new HashSet<string>();

        foreach (var prop in jsonPropertyNames)
            _ignores[type].Add(prop);
    }

    public void RenameProperty(Type type, string propertyName, string newJsonPropertyName)
    {
        if (!_renames.ContainsKey(type))
            _renames[type] = new Dictionary<string, string>();

        _renames[type][propertyName] = newJsonPropertyName;
    }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = base.CreateProperty(member, memberSerialization);

        if (IsIgnored(property.DeclaringType, property.PropertyName))
        {
            property.ShouldSerialize = i => false;
            property.Ignored = true;
        }

        if (IsRenamed(property.DeclaringType, property.PropertyName, out var newJsonPropertyName))
            property.PropertyName = newJsonPropertyName;

        return property;
    }

    private bool IsIgnored(Type type, string jsonPropertyName)
    {
        if (!_ignores.ContainsKey(type))
            return false;

        return _ignores[type].Contains(jsonPropertyName);
    }

    private bool IsRenamed(Type type, string jsonPropertyName, out string newJsonPropertyName)
    {
        Dictionary<string, string> renames;

        if (!_renames.TryGetValue(type, out renames) || !renames.TryGetValue(jsonPropertyName, out newJsonPropertyName))
        {
            newJsonPropertyName = null;
            return false;
        }

        return true;
    }
}

//忽略 Foo 示例中的 number2

public class Foo
{
public string number1 { get; set; }
public string number2 { get; set; }
public string number3 { get; set; }
}
    string Foojson = @"[
    {
        ""number1"": 1,
        ""number2"": 12345678901234567890,
        ""number3"": 3
    },
    {
        ""number1"": 9,
        ""number2"": 12345678901234567890,
        ""number3"": 8
    }
]";
var jsonResolverFoo = new PropertyRenameAndIgnoreSerializerContractResolver();
jsonResolverFoo.IgnoreProperty(typeof(Foo), "number2");
var serializerSettingsFoo = new JsonSerializerSettings();
serializerSettingsFoo.ContractResolver = jsonResolverFoo;
var deserializedJsonFoo = JsonConvert.DeserializeObject<List<Foo>>(Foojson, serializerSettingsFoo);

/* 资源链接：https://blog.rsuter.com/advanced-newtonsoft-json-dynamically-rename-or-ignore-properties-without-changing-the-serialized-class/ */

Answer 8

我遇到了类似的情况，但我的类包含 List 和 Dictionary 已填充且不应被 JSON 文件所包含的任何内容覆盖。与当时我能找到的任何其他方法相比，我更容易将数据加载到临时对象中，然后只需拉出我需要的项目。

所以对于这个例子，类似这样的东西......

public class Foo
{
    public string string1 { get; set; }
    public string string2 { get; set; }
    public string string3 { get; set; }
}
List<Foo> foos = new List<Foo>();

List<Foo> tmp= JsonConvert.DeserializeObject<List<Foo>>(json);

foreach(Foo item in tmp)
{
    foos.string1 = tmp.string1;
    foos.string3 = tmp.string3;
}