在玩bot framework时，发现他的formflow这部分的设计不错，尤其是attribute和enum的结合使用非常完美。
以下为其代码设计：
 

public enum SandwichOptions
    {
        BLT, BlackForestHam, BuffaloChicken, ChickenAndBaconRanchMelt, ColdCutCombo, MeatballMarinara,
        OvenRoastedChicken, RoastBeef, RotisserieStyleChicken, SpicyItalian, SteakAndCheese, SweetOnionTeriyaki, Tuna,
        TurkeyBreast, Veggie
    };
    public enum LengthOptions { SixInch, FootLong };
    public enum BreadOptions { NineGrainWheat, NineGrainHoneyOat, Italian, ItalianHerbsAndCheese, Flatbread };
    public enum CheeseOptions { American, MontereyCheddar, Pepperjack };
    public enum ToppingOptions
    {
        Avocado, BananaPeppers, Cucumbers, GreenBellPeppers, Jalapenos,
        Lettuce, Olives, Pickles, RedOnion, Spinach, Tomatoes
    };
    public enum SauceOptions
    {
        ChipotleSouthwest, HoneyMustard, LightMayonnaise, RegularMayonnaise,
        Mustard, Oil, Pepper, Ranch, SweetOnion, Vinegar
    };
    [Serializable]
    public class SandwichOrder
    {
        public SandwichOptions? Sandwich;
        public LengthOptions? Length;
        public BreadOptions? Bread;
        public CheeseOptions? Cheese;
        public List<ToppingOptions> Toppings;
        public List<SauceOptions> Sauce;
        public static IForm<SandwichOrder> BuildForm()
        {
            return new FormBuilder<SandwichOrder>()
                    .Message("Welcome to the simple sandwich order bot!")
                    .Build();
        }
    };


return new FormBuilder<SandwichOrder>()
                        .Message("Welcome to the sandwich order bot!")
                        .Field(nameof(Sandwich))
                        .Field(nameof(Length))
                        .Field(nameof(Bread))
                        .Field(nameof(Cheese))
                        .Field(nameof(Toppings),
                            validate: async (state, value) =>
                            {
                               //..
                                return result;
                            })
                        .Message("For sandwich toppings you have selected {Toppings}.")
                        .Field(nameof(SandwichOrder.Sauces))
                        .Field(new FieldReflector<SandwichOrder>(nameof(Specials))
                            .SetType(null)
                            .SetActive((state) => state.Length == LengthOptions.FootLong)
                            .SetDefine(async (state, field) =>
                            {
                                field
                                    .AddDescription("cookie", "Free cookie")
                                    .AddTerms("cookie", "cookie", "free cookie")
                                    .AddDescription("drink", "Free large drink")
                                    .AddTerms("drink", "drink", "free drink");
                                return true;
                            }))
                        .Confirm(async (state) =>
                        {
                            //..
                            return new PromptAttribute($"Total for your sandwich is {cost:C2} is that ok?");
                        })
                        .Field(nameof(SandwichOrder.DeliveryAddress),
                            validate: async (state, response) =>
                            {
                                //..
                                return result;
                            })
                        .Field(nameof(SandwichOrder.DeliveryTime), "What time do you want your sandwich delivered? {||}")
                        .Confirm("Do you want to order your {Length} {Sandwich} on {Bread} {&Bread} with {[{Cheese} {Toppings} {Sauces}]} to be sent to {DeliveryAddress} {?at {DeliveryTime:t}}?")
                        .AddRemainingFields()
                        .Message("Thanks for ordering a sandwich!")
                        .OnCompletion(processOrder)
                        .Build();

在以上代码中，
1. 使用了enum来定义选项信息
2. 使用attribute来做model和enum的粘合剂
3. FormBuilder的流程接口来完成对话的创建
4. FormBuilder通过对分组提问来构造不同的orderDetail对象

...
Message(..)
.Field()
...
.Message("")
.Field(...)
..