SignalsMVVM/SignalsMVVM/UI/Converters/HertzConverter.cs

using System;
using System.Globalization;
using System.Linq;
using System.Text.RegularExpressions;
using System.Windows.Data;

namespace SignalsMVVM.UI.Converters
{
    [ValueConversion(typeof(double), typeof(string))]
    public class HertzConverter : IValueConverter
    {
        static string[] keys = new string[] { "Гц", "кГц", "МГц", "ГГц" };
        static string[] keys_lower = keys.Select(k => k.ToLower()).ToArray();


        public object Convert(object value, Type targetType, object parameter, CultureInfo culture) //double->string
        {
            double _value = (double)value;
            int pow_count = 0;

            while (_value >= 1000)
            {
                _value = _value / 1000;
                pow_count++;
            }

            return _value.ToString() + " " + keys[pow_count];

        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) //string->double
        {
            #region old_code

            /*if (_value >= 500 * 1e9)
            {
                result = _value / 1e9;
                return (result.ToString() + " гГц");
            }
            else if (_value >= 1e6 & _value < 500 * 1e9)
            {
                result = _value / 1e6;
                return (result.ToString() + " мГц");
            }
            else if (_value >= 1e3 & _value < 1e6)
            {
                result = _value / 1e3;
                return (result.ToString(CultureInfo.InvariantCulture) + " кГц");
            }
            else
            {
                return (_value).ToString() + " Гц";
            }*/
            /*double result;
            if (Double.TryParse(value.ToString(), System.Globalization.NumberStyles.Any,
                         culture, out result))
            {
                return result;
            }
            else if (Double.TryParse(value.ToString().Replace(" Гц", ""), System.Globalization.NumberStyles.Any,
                         culture, out result))
            {
                return result;
            }
            else if (Double.TryParse(value.ToString().Replace(" МГц", ""), System.Globalization.NumberStyles.Any,
             culture, out result))
            {
                return result;
            }
            else if (Double.TryParse(value.ToString().Replace(" ГГц", ""), System.Globalization.NumberStyles.Any,
            culture, out result))
            {
                return result;
            }
            else if (Double.TryParse(value.ToString().Replace(" КГц", ""), System.Globalization.NumberStyles.Any,
            culture, out result))
            {
                return result;
            }*/
            #endregion

            string s = (string)value;

            Regex regex = new Regex(@"^\s*([0-9]+\.?[0-9]+)\s*([a-zA-Zа-яА-Я]+)?\s*$");
            if (!string.IsNullOrEmpty(s))
            {
                Match match = regex.Match(s);

                var groups = match.Success ? match.Groups : null;

                double savedValue = 0;
                if (groups != null)
                {
                    Group doublePart = groups[1]; Group stringPart = groups[2];

                    int index = 0;
                    if (!string.IsNullOrEmpty(stringPart.Value))
                    {
                        if (keys.Contains(stringPart.Value.ToLower()))
                            index = Array.IndexOf(keys, stringPart.Value.ToLower());
                        else
                            return 0;
                    }
                    savedValue = Math.Pow(1000, index) * System.Convert.ToDouble(doublePart.Value, CultureInfo.InvariantCulture);
                    savedValue = (savedValue > 500 * 1e9) ? 500 * 1e9 : savedValue;
                    return savedValue;
                }
            }
            return value;
        }
    }
}