Confirm Dialog In Microsoft Bot Framework

using Microsoft.Bot.Builder.FormFlow;
using System;

namespace Bot_Application1.Dialogs { [Serializable]
  public class FormFlowDemo {
    public string Name;
    public string MobileNumber;
    public string city;
    public static IForm < FormFlowDemo > GetForm() {
      return new FormBuilder < FormFlowDemo > ().Message("Welcome to support chat system. Please place your order").Field(nameof(city)).Confirm(async(state) =>{
        double minOrder = 0;
        switch (state.city) {
        case "delhi":
          minOrder = 100;
          break;
        case "gurugram":
          minOrder = 150;
          break;
        case "noida":
          minOrder = 250;
          break;
        }
        return new PromptAttribute($ "For {state.city}, the minimum order is {minOrder}. Please confirm.");
      }).Field(nameof(MobileNumber)).Field(nameof(Name)).Confirm("Thank you {Name}. Your order is placed. We will deliver your order to {city} in approx. 1 hour").Build();
    }
  }
}

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