问题描述
我正在尝试序列化我的结构,以便没有获得值的字符串获得它们的默认值 "" 而不是 null
I'm trying to serialize my struct so that the strings that didn't get a value get their default value "" instead of null
[JsonProperty(PropertyName = "myProperty", DefaultValueHandling = DefaultValueHandling.Populate)] [DefaultValue("")] public string MyProperty{ get; set; }
我在 Json 字符串中的结果:
My result in the Json string:
"myProperty": null,
我想要什么
"myProperty": "",
我也尝试创建一个没有任何效果的转换器,can Convert 和 WriteJson 函数由于某种原因甚至没有触发:
I also tried creating a converter without any effect, the can Convert and WriteJson functions aren't even firing for some reason:
[JsonProperty(PropertyName = "myProperty")] [JsonConverter(typeof(NullToEmptyStringConverter))] public string MyProperty{ get; set; } class NullToEmptyStringConverter : JsonConverter { public override bool CanConvert(Type objectType) { return objectType == typeof(object[]); } public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) { throw new NotImplementedException(); } public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { if (value == null) writer.WriteValue(""); } }
这对 Json.Net 如何反序列化 null 没有帮助作为空字符串?
推荐答案
这应该有效:
var settings = new JsonSerializerSettings() { ContractResolver= new NullToEmptyStringResolver() }; var str = JsonConvert.SerializeObject(yourObj, settings);
<小时>
public class NullToEmptyStringResolver : Newtonsoft.Json.Serialization.DefaultContractResolver { protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization) { return type.GetProperties() .Select(p=>{ var jp = base.CreateProperty(p, memberSerialization); jp.ValueProvider = new NullToEmptyStringValueProvider(p); return jp; }).ToList(); } } public class NullToEmptyStringValueProvider : IValueProvider { PropertyInfo _MemberInfo; public NullToEmptyStringValueProvider(PropertyInfo memberInfo) { _MemberInfo = memberInfo; } public object GetValue(object target) { object result = _MemberInfo.GetValue(target); if (_MemberInfo.PropertyType == typeof(string) && result == null) result = ""; return result; } public void SetValue(object target, object value) { _MemberInfo.SetValue(target, value); } }