Question

我正在创建一个MVC应用程序，它接受每日用户输入并将其放入表中。它分为几天，几周和几个月，我正在尝试使用复合键，但是我收到了错误。

以下是我的模特：

Year型号：

public class Year
{
    [ForeignKey("YearID")]
    public int YearID { get; set; }

    public virtual ICollection<Week> Weeks { get; set; }
}

Week型号：

public class Week
{
    [Key, Column(Order = 1)]
    public int WeekID { get; set; }

    [Key, Column(Order = 2)]
    public int YearID { get; set; }

    public virtual Year year { get; set; }
    public virtual ICollection<Day> Days { get; set; }
}

最后，Day模型：

public class Day
{
    [Key, Column(Order = 1)]
    public int DayID { get; set; }

    [Key, Column(Order = 2)]
    public int WeekID { get; set; }

    [Key, Column(Order = 3)]
    public int YearID { get; set; }

    public float Reading1 { get; set; }
    public float Reading2 { get; set; }
    public virtual Week Weeks { get; set; }
}

UtilityInitializer上课：

namespace Utility3.DAL
{
    public class UtilityInitializer : System.Data.Entity.DropCreateDatabaseAlways<UtilityContext>
        {
        protected override void Seed(UtilityContext context)
        {
            var years = new List<Year>
            {
                new Year{YearID = 2014},
                new Year{YearID = 2015}
            };
            years.ForEach(s => context.Years.Add(s));
            context.SaveChanges();

            var weeks = new List<Week>
            {
                new Week{WeekID = 1, YearID = 2014},
                new Week{WeekID = 2, YearID = 2014},
                new Week{WeekID = 1, YearID = 2015},
                new Week{WeekID = 2, YearID = 2015}
            };
            weeks.ForEach(s => context.Weeks.Add(s));
            context.SaveChanges();


            var days = new List<Day>
            {
                new Day{DayID = 1, WeekID = 1, YearID = 2014},
                new Day{DayID = 2, WeekID = 1, YearID = 2014},
                new Day{DayID = 1, WeekID = 2, YearID = 2014},
                new Day{DayID = 2, WeekID = 2, YearID = 2014},
                new Day{DayID = 1, WeekID = 1, YearID = 2015},
                new Day{DayID = 2, WeekID = 1, YearID = 2015},
                new Day{DayID = 1, WeekID = 2, YearID = 2015},
                new Day{DayID = 2, WeekID = 2, YearID = 2015}

            };

            days.ForEach(s => context.Days.Add(s));
            context.SaveChanges();


        }
    }
}

当我尝试制作控制器时，我收到此错误：

Unable to retrieve metadata from "Utility3.Models.Year". The property "YearID" cannot be configured as a navigation property. The property must be a valid entity type and the property should have a non-abstract getter and setter. For collection properties the type must implement ICollection<T> where T is a valid entity type.

我尝试YearID作为外键来解决问题。没有外键我得到了一个不同的错误。

为什么YearID会抛出该错误？

修改我尝试将Week YearID模型中的名称更改为YearNo，并在初始化程序中更改了此段代码：

var weeks = new List<Week>
        {
            new Week{YearNo = years.Single(i => i.YearID == 2014).YearID, WeekID = 1},
            new Week{YearNo = years.Single(i => i.YearID == 2014).YearID, WeekID = 2},
            new Week{YearNo = years.Single(i => i.YearID == 2015).YearID, WeekID = 1},
            new Week{YearNo = years.Single(i => i.YearID == 2015).YearID, WeekID = 2}
        };
        weeks.ForEach(s => context.Weeks.Add(s));
        context.SaveChanges();

但是现在告诉我序列中没有匹配的元素但是有？

Answer 1

我设法通过将[DatabaseGenerated(DatabaseGeneratedOption.None)]添加到键上方的模型来让它工作，以便我可以编辑它们。它现在以任何方式工作。

Answer 2

不应将外键用作表上组合键的一部分。改变你的表格就像这样工作，它会做你想做的事。

public class Year
{
    [Key]
    public int YearID { get; set; }

    public virtual ICollection<Week> Weeks { get; set; }
}


public class Week
{
    [Key]
    public int WeekID { get; set; }

    public virtual Year year { get; set; }
    public virtual ICollection<Day> Days { get; set; }
}

public class Day
{
    [Key]
    public int DayID { get; set; }

    public float Reading1 { get; set; }
    public float Reading2 { get; set; }
    public virtual Week Weeks { get; set; }
}

复合关键问题

2 个答案: