using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        NumberFormatInfo provider = new NumberFormatInfo();

        provider.NumberDecimalDigits = 2;

        provider.NumberDecimalSeparator = ",";

        provider.NumberGroupSeparator = ".";

        provider.NumberGroupSizes = new int[] { 3 };

        string strValue = "1.799,53";

        double result = Convert.ToDouble(strValue, provider);

        Console.WriteLine(result.ToString());

        strValue = "17999,55";

        result = Convert.ToDouble(strValue, provider);

        Console.WriteLine(result.ToString());

        strValue = "1.799,00";

        result = Convert.ToDouble(strValue, provider);

        Console.WriteLine(result.ToString());

        strValue = "1.800";

        result = Convert.ToDouble(strValue, provider);

        Console.WriteLine(result.ToString());

    }

}