using System;

public class Program

{

    public static void Main()

    {

        var test = Eva("500000.00");

        Console.WriteLine(test);

    }

    public static string Eva(object value)

    {

        var stringValue = value.ToString();

        var decimalValue = System.Convert.ToDecimal(stringValue);

        var specifier = "0,0.000";

        return decimalValue.ToString(specifier);

    }

}