JsonConvert.SerializeObject 空值处理

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

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, null);
if (_MemberInfo.PropertyType == typeof(string) && result == null) result = "";
return result;

}

public void SetValue(object target, object value)
{
_MemberInfo.SetValue(target, value,null);
}
}