Sequence包含多个元素MVC [英] Sequence contains more than one element MVC

问题描述

什么可能是错的。它正常工作，直到我添加新属性'国家'然后添加迁移。以及如何在屏幕中为所有团队对象添加国家/地区并创建新团队。重建。更新数据库，我得到错误

 public static List< Team> GetTeams（）
 {
 List< Team> teams = new List< Team>（）
 {
 new Team（）
 {
 TeamName =Canucks，
 City =Vancouver，
省=BC，
国家=加拿大
}，
新团队（）
 {
 TeamName =Oilers，
 City =埃德蒙顿，
省=艾伯塔省，
国家=加拿大
}，
新队伍（）
 {
 TeamName = Flames，
 City =Calgary，
 Province =Alberta，
 Country =Canada
}，
 new Team（）
 {
 TeamName =Sharks，
 City =San Jose，
省=加利福尼亚，
国家=美国
} 
}; 
返回队伍; 
} 
 

这个新房产的地方如下：

公共课团队
 {
 [Key] 
 [MaxLength（10）] 
 public string TeamName {get;组; } //主键
 public string City {get;组; } 
 public string Province {get;组; } 
 public string Country {get;组; } 
 
 public List< Player>玩家{得到;组; } //团队与玩家/团队的关系可以有多个玩家
} 

我尝试过：



我在互联网上发现的一切都依赖于FirstOrDefault。但我不使用这个

解决方案

你使用EF吗？如果是，则从数据库更新模型并查看结果。

what can be wrong. it works properly untill I add new property 'Country' then add-migration. and how in screen I add for all team objects a country and create new team. rebuild. update-database and i get mistake

public static List<Team> GetTeams()
     {
         List<Team> teams = new List<Team>()
         {
             new Team()
             {
                 TeamName = "Canucks",
                 City = "Vancouver",
                 Province = "BC",
                 Country = "Canada"
             },
             new Team()
             {
                 TeamName = "Oilers",
                 City = "Edmonton",
                 Province = "Alberta",
                 Country = "Canada"
             },
             new Team()
             {
                 TeamName = "Flames",
                 City = "Calgary",
                 Province = "Alberta",
                 Country = "Canada"
             },
             new Team()
             {
                 TeamName = "Sharks",
                 City = "San Jose",
                 Province = "California",
                 Country = "USA"
             }
         };
         return teams;
     }

the place with new property loocks like this:

public class Team
    {
        [Key]
        [MaxLength(10)]
        public string TeamName { get; set; } //primary key
        public string City { get; set; }
        public string Province { get; set; }
        public string Country { get; set; }

        public List<Player> Players { get; set; }//team has relationship with player/ team can have multuply players
    }

What I have tried:

All i found on the internet depence on FirstOrDefault. But I don't use this

解决方案

Are you using EF? If yes then update the model from database as well and see the result.

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