public static void Main()
var testNumber = (decimal)1.23456789;
var lotSize = (decimal)0.00000100;
var decimalSpaces = lotSize.ToString()
var pow = (decimal)Math.Pow(10, decimalSpaces);
var result = Math.Floor(testNumber * pow) / pow;
Console.WriteLine(result);
lotSize = (decimal)1.00000000;
decimalSpaces = lotSize.ToString()
pow = (decimal)Math.Pow(10, decimalSpaces);
result = Math.Floor(testNumber * pow) / pow;
Console.WriteLine(result);