using System;

using System.Globalization;

using System.Threading;

​

public class Program

{   

    public static void Main()

    {       

        var numberFormatInfo = new NumberFormatInfo();

        numberFormatInfo.NumberDecimalSeparator = "#";

        string s1 = "2"; 

        string s2 = "25#00";

​

        double d1 = Convert.ToDouble(s1, numberFormatInfo);

        double d2 = Convert.ToDouble(s2, numberFormatInfo);

        double d3 = d2 * d1;

        Console.WriteLine(d3);

    }

}