CODEWITHSUNDEEP
sql-serverentity-frameworkef-code-first
user1630359
user1630359

Reputation: 103

Entity Framework Code First - One to Many relations from multiple tables

I have a BlobEntity table that contains paths to files for many other tables (tableX, tableY, tableZ, etc...) in my application.

The relation between all the other tables to BlobEntity table is one to many.

Example:

tableX -> BlobTable (OTM)

tableY -> BlobTable (OTM)

tableZ -> BlobTable (OTM)

and the relation is:

public virtual ICollection<BlobEntity> BlobEntity { get; set; }

I'm not sure if this is an issue, but entity framework Code First creates a new FK column in BlobEntity table for each source table.

In my case, BlobEntity contains three FK columns for tableX, tableY and tableZ.

In order to be efficiency, i rather create one column in BlobEntity that contains the FK for the source tables.

Is it reasonable?

Please advise...

Thanks.

Upvotes: 1

Views: 344

Answers (1)

Luca Ghersi
Luca Ghersi

Reputation: 3321

No, you can't do this even in plain old SQL. You can have a foreing key pointing to more than one table; that's why you need three columns.

If you want to do a "trick" like this, you have to manually manage the relation (I mean, no real FK), but you can't map it into EF.

What about this?

public class EntityA
{
    public int Id { get; set; }

    public int MyFileID {get;set;}
    public virtual MyFiles MyFile { get; set; }
}

public class EntityB
{
    public int Id { get; set; }

    public int MyFileID {get;set;}
    public virtual MyFiles MyFile { get; set; }
}

public class MyFiles
{
    public MyFiles()
    {
        // ReSharper disable once VirtualMemberCallInContructor
        FilesForEntityA = new List<EntityA>();
        // ReSharper disable once VirtualMemberCallInContructor
        FilesForEntityB = new List<EntityB>();
    }


    public int Id { get; set; }

    public int? EntityAId {get;set;}
    public int? EntityBId {get;set;}

    public virtual ICollection<EntityA> FilesForEntityA { get; set; }
    public virtual ICollection<EntityB> FilesForEntityB { get; set; }
}

This way you can have the FK in place and you can easily manager multiple entities. Obviously if you have many files for each entity, you can go with a N-to-N relationship, like this.

Upvotes: 2

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