实体框架6表具有许多外键，每个外键指向不同的表

Question

I have Country, City, Region and "Account Address" tables.

I want to create foreign key columns in "Account Address" pointing to Country, City, Region tables.

I have this code but it throws an error on creating database

The property \'Account_Id\' 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

After New Edit

public class Cities
{
    [Key]
    public int City_Id { get; set; }
    public string City_name { get; set; }
    public int Country_Id { get; set; }

    [ForeignKey("Country_Id")]
    public Countries countries { get; set; }
}

public class Region
{
    [Key]
    public int Region_Id { get; set; }
    public string Region_name { get; set; }
    public int City_Id { get; set; }

    [ForeignKey("City_Id")]
    public Countries countries { get; set; }
}

public class Accounts
{
    [Key]
    public int Account_Id { get; set; }
    public string Fullname { get; set; }
    public string Email { get; set; }
    public string password { get; set; }
    public int Cell_phone { get; set; }
    public string Role { get; set; }
    public int? estate_office_Id { get; set; }

    [ForeignKey("estate_office_Id")]
    public Estate_office estate_office { get; set; }

    public List<Ads> ads { get; set; }
}

public class Account_address
{
    [Key]
    public int Id { get; set; }

    [ForeignKey("Account_Id"), Column(Order = 0)]
    public int Account_Id { get; set; }

    [ForeignKey("Country_Id"), Column(Order = 1)]
    public int Country_Id { get; set; }

    [ForeignKey("City_Id"), Column(Order = 2)]
    public int City_Id { get; set; }

    [ForeignKey("Region_Id"), Column(Order = 3)]
    public int Region_Id { get; set; }

    public Accounts accounts { get; set; }
    public Countries countries { get; set; }
    public Cities cities { get; set; }
    public Region region { get; set; }
}

Answer 1

You need to define public properties as shown below on the Account_address class.Then only EF will know how to map those navigation properties correctly.

  public class Account_address
   {
    ......
    ......


    public  Accounts accounts { get; set; } //like this
    public  Countries countries { get; set; } //like this
    public  Cities cities { get; set; } //like this
    public  Region region { get; set; } //like this
  }

Update :

Hence you're not using singular naming convention for the classes,you have encountered this issue.Either you have to change the name of classes as singular or need to change the navigational property names a shown below.You have to do this for all the places.Here I have shown only for the Accounts class related navigational property.

    [ForeignKey("Accounts_Id"), Column(Order = 0)]
    public int Accounts_Id { get; set; }

My Advice is to follow the basic naming conventions .Then you can avoid lot of above kind of weird errors.