using System;

​

public class Program

{

    public static void Main()

    {

        string yourAppVersion = "4.0.19903";

        if (CheckVersion(yourAppVersion))

            throw new Exception("Client app version is not compatible with API version.");

        Console.WriteLine();

    }

​

    private static bool CheckVersion(string version)

    {

        Version clientAppVersion = new Version(version);

        Version minimumVersionInDb = new Version("4.0.1");

        return clientAppVersion.CompareTo(minimumVersionInDb) != -1;

    }

}