IsoDateTimeConverter timeConverter = new IsoDateTimeConverter();timeConverter.DateTimeFormat = "yyyy-MM-dd HH:mm:ss";// IsoDateTimeConverter timeConverter = new IsoDateTimeConverter { DateTimeFormat = "yyyy-MM-dd HH:mm:ss"};string jsonStr = JsonConvert.SerializeObject(obj,Formatting.Indented,timeConverter);

NewtonSoft.Json NULL转空字符串

/// 
/// 对DBNull的转换处理，此处只写了转换成JSON字符串的处理，JSON字符串转对象的未处理/// 
public class DBNullCreationConverter : JsonConverter{    /// 
    /// 是否允许转换    /// 
    public override bool CanConvert(Type objectType)    {        bool canConvert = false;        switch (objectType.FullName)        {            case "System.DBNull":                canConvert = true;                break;        }        return canConvert;    }    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)    {        return existingValue;    }    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)    {        writer.WriteValue(string.Empty);    }    public override bool CanRead    {        get        {            return false;        }    }    /// 
    /// 是否允许转换JSON字符串时调用    /// 
    public override bool CanWrite    {        get        {            return true;        }    }}

IsoDateTimeConverter timeFormat = new IsoDateTimeConverter();DBNullCreationConverter d = new DBNullCreationConverter();timeFormat.DateTimeFormat = "yyyy-MM-dd HH:mm:ss";var json = JsonConvert.SerializeObject(ds.Tables, Newtonsoft.Json.Formatting.Indented, timeFormat, d);