How to create Lookup table and define relationship

问题:

As you can see at below, there are a Lookup table for the enum values and I want to create a relationship between a table's enum values and LookupKey column of the Lookup table (instead of ID column of the Lookup table).

Lookup table:

ID   | LookupType | LookupKey | LookupValue |
101  | Status     | 0         | Passive     | 
106  | Gender     | 1         | Male        | 
113  | Status     | 1         | Active      | 
114  | Gender     | 2         | Female      | 
118  | Status     | 2         | Cancelled   | 

Main Table:

ID | Status     | Gender    | Name              | ...
1  | 0          | 1         | John Smith        | ...
2  | 1          | 2         | Christof Jahnsen  | ...
3  | 2          | 1         | Alexi Tenesis     | ...
4  | 0          | 2         | Jurgen Fechtner   | ...
5  | 1          | 2         | Andreas Folk      | ...

However, when using PK-FK relation and InverseProperty as on DataAnnotations - InverseProperty Attribute the relation is created with the ID column of the Lookup table and I cannot make the relation to the LookupKey column. Could you give an example how to achieve this?

回答1:

We have a common lookup table here. It looks simlar to yours. LookupData has a primary key and a foreign key to LookupTypes which is equivalent to your enum and the value. We might also have some other simple fields like a flag or code which are identified in the LookupType metadata table. Then in out main table we might have "GenderLookupId" which points to the LookupData.Id field. The IDs themselves have no meaning and can be entered in any order. If you want gender 1 and 2 to have meaning, you should probably add another attribute for that (see surrogate keys).

Example with data:

LookupType

ID    Description    CodeDesc        BooleanDesc  
1     Genders        Gender Code     NULL
2     Races          Race Code       Is Active

LookupData

ID    LookupTypeId    Description    Code    Boolean
789   1               Male           M       NULL
790   2               White          W       True
791   1               Female         F       NULL
792   2               Hispanic       H       False

Main Name Table

NameId   Name          GenderLookupId   RaceLookupId
1234     Joe Smith     789              790
1235     Mary Meyers   791              792

Classes:

public class LookupType
{
    public int Id { get; set; }
    public string Description { get; set; }
    public string CodeDescription { get; set; }
    public string BooleanDescription { get; set; }

}

public class LookupData
{
    public int Id { get; set; }
    public int LookupTypeId { get; set; }
    public string Description { get; set; }
    public string Code { get; set; }
    public bool? BooleanValue { get; set; }
    public LookupType LookupType { get; set; } 

}

public class Name
{
    public int Id { get; set; }
    public string FullName { get; set; }
    public int? GenderLookupId { get; set; }
    public LookupData Gender { get; set; } 
}

LookupData Config:

HasRequired(p => p.LookupType).WithMany(p=>p.LookupData).HasForeignKey(p=>p.LookupTypeId).WillCascadeOnDelete(false);

Name Config:

HasOptional(p => p.Gender).WithMany(p=>p.Name).HasForeignKey(p=>p.GenderLookupId).WillCascadeOnDelete(false);