"Double ToString Extension"

public static class DoubleExtensions {
	public static string ToString(this double @this, int numDecimalPlaces) {
		return @this.ToString("N" + numDecimalPlaces.ToString(CultureInfo.InvariantCulture), CultureInfo.InvariantCulture); 
	}
}

// ... Elsewhere ...

// Will write something like "3.5"; assuming YearsWorkedAtCompany is a double:
Console.WriteLine(user.YearsWorkedAtCompany.ToString(1));