Use standard numeric format specifiers.
using System; using System.Globalization; public class Example { public static void Main() { float value = 12345.12345F; string specifier; CultureInfo culture; specifier = "G"; culture = CultureInfo.CreateSpecificCulture("eu-ES"); Console.WriteLine(value.ToString(specifier, culture)); Console.WriteLine(value.ToString(specifier, CultureInfo.InvariantCulture)); } } //12345,12 //12345.12