public class GenericListTypeConverter<T> : TypeConverter
    {
        protected readonly TypeConverter typeConverter;

        public GenericListTypeConverter()
        {
            typeConverter = TypeDescriptor.GetConverter(typeof(T));
            if (typeConverter == null)
                throw new InvalidOperationException("No type converter exists for type " + typeof(T).FullName);
        }

        protected virtual string[] GetStringArray(string input)
        {
            if (!String.IsNullOrEmpty(input))
            {
                string[] result = input.Split(',');
                Array.ForEach(result, s => s.Trim());
                return result;
            }
            else
                return new string[0];
        }

        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {

            if (sourceType == typeof(string))
            {
                string[] items = GetStringArray(sourceType.ToString());
                return items.Any();
            }

            return base.CanConvertFrom(context, sourceType);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string)
            {
                string[] items = GetStringArray((string)value);
                var result = new List<T>();
                Array.ForEach(items, s =>
                {
                    object item = typeConverter.ConvertFromInvariantString(s);
                    if (item != null)
                    {
                        result.Add((T)item);
                    }
                });

                return result;
            }
            return base.ConvertFrom(context, culture, value);
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                string result = string.Empty;
                if (((IList<T>)value) != null)
                {
                    //we don't use string.Join() because it doesn't support invariant culture
                    for (int i = 0; i < ((IList<T>)value).Count; i++)
                    {
                        var str1 = Convert.ToString(((IList<T>)value)[i], CultureInfo.InvariantCulture);
                        result += str1;
                        //don't add comma after the last element
                        if (i != ((IList<T>)value).Count - 1)
                            result += ",";
                    }
                }
                return result;
            }

            return base.ConvertTo(context, culture, value, destinationType);
        }
    }

    public class ShippingOptionTypeConverter : TypeConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            if (sourceType == typeof(string))
            {
                return true;
            }

            return base.CanConvertFrom(context, sourceType);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string)
            {
                ShippingOption shippingOption = null;
                string valueStr = value as string;
                if (!String.IsNullOrEmpty(valueStr))
                {
                    try
                    {
                        using (var tr = new StringReader(valueStr))
                        {
                            var xmlS = new XmlSerializer(typeof(ShippingOption));
                            shippingOption = (ShippingOption)xmlS.Deserialize(tr);
                        }
                    }
                    catch
                    {
                        //xml error
                    }
                }
                return shippingOption;
            }
            return base.ConvertFrom(context, culture, value);
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                var shippingOption = value as ShippingOption;
                if (shippingOption != null)
                {
                    var sb = new StringBuilder();
                    using (var tw = new StringWriter(sb))
                    {
                        var xmlS = new XmlSerializer(typeof(ShippingOption));
                        xmlS.Serialize(tw, value);
                        string serialized = sb.ToString();
                        return serialized;
                    }
                }
                else
                {
                    return "";
                }
            }

            return base.ConvertTo(context, culture, value, destinationType);
        }
    }

    public class ShippingOptionListTypeConverter : TypeConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            if (sourceType == typeof(string))
            {
                return true;
            }

            return base.CanConvertFrom(context, sourceType);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string)
            {
                List<ShippingOption> shippingOptions = null;
                string valueStr = value as string;
                if (!String.IsNullOrEmpty(valueStr))
                {
                    try
                    {
                        using (var tr = new StringReader(valueStr))
                        {
                            var xmlS = new XmlSerializer(typeof(List<ShippingOption>));
                            shippingOptions = (List<ShippingOption>)xmlS.Deserialize(tr);
                        }
                    }
                    catch
                    {
                        //xml error
                    }
                }
                return shippingOptions;
            }
            return base.ConvertFrom(context, culture, value);
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                var shippingOptions = value as List<ShippingOption>;
                if (shippingOptions != null)
                {
                    var sb = new StringBuilder();
                    using (var tw = new StringWriter(sb))
                    {
                        var xmlS = new XmlSerializer(typeof(List<ShippingOption>));
                        xmlS.Serialize(tw, value);
                        string serialized = sb.ToString();
                        return serialized;
                    }
                }
                else
                {
                    return "";
                }
            }

            return base.ConvertTo(context, culture, value, destinationType);
        }
    }

    public static class ExtensionMethods
    {
        #region 转换函数
        /// <summary>
        /// object 转换为 int
        /// </summary>
        /// <returns></returns>
        private static int ObjToInt(object obj)
        {
            if (obj == null)
                return 0;
            if (obj.Equals(DBNull.Value))
                return 0;

            int returnValue;

            if (int.TryParse(obj.ToString(), out returnValue))
            {
                return returnValue;
            }
            else
            {
                return 0;
            }
        }

        /// <summary>
        /// 转换为boolean型
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static bool ObjToBool(object obj)
        {
            if (obj == null)
                return false;
            if (obj.Equals(DBNull.Value))
                return false;

            bool returnValue;

            if (bool.TryParse(obj.ToString(), out returnValue))
            {
                return returnValue;
            }
            else
            {
                return false;
            }
        }

        /// <summary>
        /// object 转换为 int?
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static int? ObjToIntNull(object obj)
        {
            if (obj == null)
                return null;
            if (obj.Equals(DBNull.Value))
                return null;

            return ObjToInt(obj);
        }


        /// <summary>
        /// object 转换为 string
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static string ObjToStr(object obj)
        {
            if (obj == null)
                return "";
            if (obj.Equals(DBNull.Value))
                return "";
            return Convert.ToString(obj);
        }


        /// <summary>
        /// object 转换为 decimal
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static decimal ObjToDecimal(object obj)
        {
            if (obj == null)
                return 0;
            if (obj.Equals(DBNull.Value))
                return 0;

            try
            {
                return Convert.ToDecimal(obj);
            }
            catch
            {
                return 0;
            }
        }

        /// <summary>
        /// object 转换为 decimal?
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static decimal? ObjToDecimalNull(object obj)
        {
            if (obj == null)
                return null;
            if (obj.Equals(DBNull.Value))
                return null;

            return ObjToDecimal(obj);
        }


        /// <summary>
        /// 转换为日期
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        private static DateTime? ObjToDateNull(object obj)
        {
            if (obj == null)
            {
                return null;
            }
            try
            {
                return Convert.ToDateTime(obj);
            }
            catch
            {
                return null;
            }
        }
        #endregion

        #region 数据转换扩展函数

        /// <summary>
        /// object 转换为 int
        /// </summary>
        /// <returns></returns>
        public static int ToInt(this object obj)
        {
            return ObjToInt(obj);
        }

        /// <summary>
        /// object 转换为 string
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static string ToStr(this object obj)
        {
            return ObjToStr(obj);
        }

        /// <summary>
        /// object 转换为 decimal
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static decimal ToDecimal(this object obj)
        {
            return ObjToDecimal(obj);
        }

        /// <summary>
        /// object 转换为 int?
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static int? ToIntNull(this object obj)
        {
            return ObjToIntNull(obj);
        }

        /// <summary>
        /// object 转换为 decimal?
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static decimal? ToDecimalNull(this object obj)
        {
            return ObjToDecimalNull(obj);
        }

        /// <summary>
        /// 转换为boolean型
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static bool ToBool(this object obj)
        {
            return ObjToBool(obj);
        }

        /// <summary>
        /// 转换为日期
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static DateTime? ToDateNull(this object obj)
        {
            return ObjToDateNull(obj);
        }

        /// <summary>
        /// 转换为Double
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static double ToDouble(this decimal value)
        {
            return Convert.ToDouble(value);
        }
        #endregion
    }