using System.Globalization;
public static void Main()
string FormattedText = "";
string fieldText = "123456789.123446789";
foreach (char c in fieldText)
dblValue = (dblValue * 10.0) + (c - '0');
divideBy = divideBy * 10.0;
amount = dblValue / divideBy;
amount = Math.Round(amount, 4, MidpointRounding.AwayFromZero);
FormattedText = string.Format(CultureInfo.CurrentCulture, "{0:0.0000}", amount);
Console.WriteLine(FormattedText);