Newtonsoft.Json 序列化字符串null转换成""

Newtonsoft.Json 中把不赋值的字符串属性序列成空串，直接上代码如下 ：

var settings = new JsonSerializerSettings() { ContractResolver= new NullToEmptyStringResolver() };
var str = JsonConvert.SerializeObject(yourObj, settings);

using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
using System.Reflection;

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);
    }
}

原文地址：https://stackoverflow.com/questions/23830206/json-convert-empty-string-instead-of-null