public ConsoleMenu(System.IO.Stream outputStream, System.IO.Stream inputStream)
    {
        if (!typeof(T).IsEnum)
        {
            throw new TypeAccessException("Type" + typeof(T).Name + "must be of type Enum!");
        }

        OutputStream = outputStream;
        InputStream = inputStream;
    }

    public void ShowMenu(bool parseUnderlinetoWhitespace = true)
    {
        this.CheckStreams();

        var streamWriter = new System.IO.StreamWriter(this.OutputStream) { AutoFlush = true };
        var memberInfos = typeof(T).GetMembers(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static);

        foreach (var memberInfo in memberInfos)
        {
            var menuEntryText = memberInfo.Name;
            var menuEntryNumber = (int)Enum.Parse(typeof(T), memberInfo.Name);

            streamWriter.WriteLine("{0} - {1}", menuEntryNumber, menuEntryText);
        }

        streamWriter.WriteLine();
    }

    private void CheckStreams()
    {
        if (InputStream == null)
        {
            throw new NullReferenceException("InputStream must be a valid stream!");
        }
        if (OutputStream == null)
        {
            throw new NullReferenceException("OutputStream must be a valid stream!");
        }
    }

    public enum Products
    {
        Display_Product = 1,
        Add_Product = 2,
        Edit_Product = 3,
        Delete_Product = 4,
        Search_Product = 5,
        Exit = 6
    }
}

public class Product
{
    public string Name { get; set; }
    public decimal Quantity { get; set; }
}

public class Inventory
{
    private List<Product> Products { get; set; }

    public int Count { get { return this.Products.Count; } }

    public IEnumerable<Product> GetAllProducts()
    {
        return this.Products.AsReadOnly();
    }

    public void RemoveByName(string productName)
    {
        var p = this.FindByName(productName);
        if (p != null) Products.Remove(p);
    }

    public void AddProduct(string productName, decimal productQuantity)
    {
        Products.Add(new Product() { Name = productName, Quantity = productQuantity });
    }

    public Product FindByName(string productName)
    {
        foreach (Product p in this.Products)
        {
            if (p.Name == productName)
            {
                return p;
            }
        }
        return null;
    }
}

class Program
{
    //The program starts here.
    static void Main(string[] args)
    {
        string valueString = "Welcome to Swedish Mosaic AB Ordersystem";
        Console.WriteLine(valueString);

        string username, password;
        Console.Write("Administrator Username: ");
        username = Console.ReadLine();

        Console.Write("Enter your password: ");
        password = Console.ReadLine();
        Console.WriteLine("============");
        if (username == "Mosaic" && password == "123")
        {
            Console.WriteLine("Login successful");
        }
        else
        {
            Console.WriteLine("Login failed!");
        }
        if (bool true)

    }



    public static void MainMenu(string[] args)
    {
        var category = 0;
        var menuOption = new string[] { "Display Product", "Add Product", "Edit Product", "Delete Product", "Search Product", "Exit" };
        var methodCall = new string[] { "Display Product", "Add Product", "Edit Product", "Delete Product", "Search Product", "Exit" };
        do
        {
            category = Menu("MainMenu", menuOption, methodCall);

            Console.WriteLine("You choose: {0}", category);
        }
        while (category != 0);
    }

    static int Menu(string titel, string[] alternativ)
    {
        return DisplayAlternativ(titel, alternativ);
    }

    static int Menu(string titel, string[] alternativ, string [] metod)
    {
        var val = DisplayAlternativ(titel, alternativ);
        if (val == 0)
            return 0;

        Program p = new Program();
        Type t = p.GetType();
        var methodCall = metod[val - 1];
        MethodInfo mi = t.GetMethod(methodCall, BindingFlags.NonPublic | BindingFlags.Instance);
        string result = mi.Invoke(p, new object[] { 1 }).ToString();

        return val;
    }

    static int DisplayAlternativ(String titel, string[] alternativ)
    {
        Console.WriteLine(titel);
        Console.WriteLine();
        for (int i = 0; i < alternativ.Count(); i++)
        {
            Console.WriteLine("{0} - {1}", i + 1, alternativ[i]);
        }
        Console.WriteLine();
        Console.WriteLine("0 - Avsluta");
        bool conversionOK;
        var val = -1;
        do
        {
            var read = Console.ReadLine();
            conversionOK = int.TryParse(read, out val);
            if (conversionOK == true && val == 0)
                return 0;
            if (conversionOK == true && val >= 1 && val <= alternativ.Count())
                break;
            Console.WriteLine("Wrong input: " + read);
        } while (true);
        return val;
    }

    int DisplayProduct(int arg = 1)
    {
        Console.WriteLine("Display Product");
        return 1;
    }

    int AddProduct(int arg = 1)
    {
        Console.WriteLine("AddProduct");
        return 1;
    }

    int EditProduct(int arg = 1)
    {
        Console.WriteLine("EditProduct");
        return 1;
    }

    int DeleteProduct(int arg = 1)
    {
        Console.WriteLine("Delete Product");
        return 1;
    }

    int SearchProduct(int arg = 1)
    {
        Console.WriteLine("SearchProduct");
        return 1;
    }

    int Exit(int arg = 1)
    {
        Console.WriteLine("Exit");
        return 1;
    }

    Console.WriteLine("Category selected");

    Console.ReadKey();
}