You should use
Decimal.TryParse Method[
^]
++++++++++++++++++++++++++++++++
Example added as requested:
using System;
public class Program
{
public static void Main()
{
string str = "123.45";
Decimal num;
if (Decimal.TryParse(str, out num))
Console.WriteLine(num);
else
Console.WriteLine("Unable to parse '{0}'.", str);
}
}