Net Core 下 Newtonsoft.Json 转换字符串 null 替换成string.Empty

 public class NullToEmptyStringResolver : DefaultContractResolver ???{ ???????/// <summary> ???????/// 创建属性 ???????/// </summary> ???????/// <param name="type">类型</param> ???????/// <param name="memberSerialization">序列化成员</param> ???????/// <returns></returns> ???????protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization) ???????{ ???????????return type.GetProperties() ???????????????.Select(x => ???????????????{ ???????????????????var property = CreateProperty(x, memberSerialization); ???????????????????property.ValueProvider = new NullToEmptyStringValueProvider(x); ???????????????????return property; ???????????????}).ToList(); ???????} ???????/// <inheritdoc /> ???????/// <summary> ???????/// 小写 ???????/// </summary> ???????/// <param name="propertyName"></param> ???????/// <returns></returns> ???????protected override string ResolvePropertyName(string propertyName) ???????{ ???????????return propertyName.ToLower(); ???????} ???}

public class NullToEmptyStringValueProvider : IValueProvider ???{ ???????private readonly PropertyInfo _memberInfo; ???????/// <summary> ???????/// 构造函数 ???????/// </summary> ???????/// <param name="memberInfo"></param> ???????public NullToEmptyStringValueProvider(PropertyInfo memberInfo) ???????{ ???????????_memberInfo = memberInfo; ???????} ???????/// <inheritdoc /> ???????/// <summary> ???????/// 获取Value ???????/// </summary> ???????/// <param name="target"></param> ???????/// <returns></returns> ???????public object GetValue(object target) ???????{ ???????????var result = _memberInfo.GetValue(target); ???????????if (_memberInfo.PropertyType == typeof(string) && result == Convert.DBNull) ???????????{ ???????????????result = string.Empty; ???????????} ???????????return result; ???????} ???????/// <inheritdoc /> ???????/// <summary> ???????/// 设置Value ???????/// </summary> ???????/// <param name="target"></param> ???????/// <param name="value"></param> ???????public void SetValue(object target, object value) ???????{ ???????????_memberInfo.SetValue(target, value); ???????} ???}