EntityFramework 1至0、1或许多关系

Question

I am struggling to create a relationship in Entity framework between three tables.. I am developing WPF application using C#, Sqlite 3.0 and Entity Framework 6.

I have Following tables(classes):

1. Investor
2. Investment
3. ImageStore

I want to create a model so that Investor and Investment (and future other classes) can store either 0, 1 or Many images.. (as it is obvious from class names that Investor can have only one profile image and Investment class can have multiple images) My ImageStore class looks something like this:

public class ImageStore : PropertyChangedNotification
    {
        [Key]
        public int ImageStoreId { get; set; }
        [Required]
        public string ImageFile { get; set; }
        [Required]
        public Byte[] ImageBlob { get; set; }

        public string FileName { get; set; }
        [Required]
        public int FileSize { get; set; }


        //public virtual ImageData ImageData { get; set; }
    }

In order to create 1 to 0,1 or Many relationship, I created one more intermediate table called: ImageData as seen below (I don't know whether it is really a good approach but that is only what I can think of right now..)

public class ImageData : PropertyChangedNotification
    {
        [Key]
        public int ImageDataId { get; set; }

        [ForeignKey("Investment")]
        public long? InvestmentId { get; set; }

        [ForeignKey("Investor")]
        public long? InvestorId { get; set; }

        [ForeignKey("ImageStore")]
        public int ImageStoreId { get; set; }

        public virtual ImageStore ImageStore { get; set; }

        public virtual Investment Investment { get; set; }

       public virtual Investor Investor { get; set; }
    }

My Investor class looks like this:

public class Investor : PropertyChangedNotification
    {
        [Key]
        public long InvestorId { get; set; }        

        [NotMapped]
        [ForeignKey("ImageData")]
        public List<int> ImageDataList { get; set; }

        public virtual ICollection<ImageData> ImageDataCollection { get; set; }
        public virtual ICollection<Investment> Investments { get; set; }        
    }

My Investment Class Looks like this:

 public class Investment : PropertyChangedNotification
    {
        [Key]
        public long InvestmentId { get; set; }

       [ForeignKey("Investor")]
       [Required]
       public long FirstInvestorId { get; set; }       


        [NotMapped]
        [ForeignKey("ImageData")]
        public List<int> ImageDataList { get; set; }

        public virtual ICollection<ImageData> ImageDataCollection { get; set; }       

        public virtual Investor Investor { get; set; }

        [NotMapped]
        [Required (ErrorMessage = "First Investor is Required")]
        public Investor FirstInvestor { get; set; }
    }

This is my related fluent configuration:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // MyData Database does not pluralize table names
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

            modelBuilder.Entity<Investor>().HasOptional(s => s.ImageDataCollection);
            modelBuilder.Entity<Investment>().HasOptional(s => s.ImageDataCollection);
            //modelBuilder.Conventions.Remove<IncludeMetadataConvention>();
        }

When I start debugging the application, I get the following error:

1. ImageData_Investment_Source: : Multiplicity is not valid in Role 'ImageData_Investment_Source' in relationship 'ImageData_Investment'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'
2. ImageData_Investor_Source: : Multiplicity is not valid in Role 'ImageData_Investor_Source' in relationship 'ImageData_Investor'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'

Can someone please suggest me either a solution to this problem and/or optimal approach to achieve what I need, I really will appreciate. Thanks

Answer 1

The fluent configuration

modelBuilder.Entity<Investor>().HasOptional(s => s.ImageDataCollection);
modelBuilder.Entity<Investment>().HasOptional(s => s.ImageDataCollection);

is incomplete.

Since the you already have the necessary data annotations and navigation / FK properties, you can simply remove it. Or if you want to provide fluent configuration (which I personally prefer because it allows you to specify everything explicitly and not rely on conventions and specifically for relationships, not so intuitive ForegnKey and InverseProperty data annotations), then you should make sure it reflects exactly the presense/absence of the navigation and FK properties in the involved entities.

The correct fluent configuration reflecting your model so far is like this:

modelBuilder.Entity<Investor>()
    .HasMany(e => e.ImageDataCollection)
    .WithOptional(e => e.Investor)
    .HasForeignKey(e => e.InvestorId);

modelBuilder.Entity<Investment>()
    .HasMany(e => e.ImageDataCollection)
    .WithOptional(e => e.Investment)
    .HasForeignKey(e => e.InvestmentId);