Entity Framework and One to Many Relationships Code First

Question

I have been having trouble understanding what I would think is a simple relationship model. I have a CloudFile object that represents a file on a CDN. I have two other objects, Creative and Merchant , that relate to the CloudFile .

My CloudFile Class

public class CloudFile
{
    [Key]
    public int CloudFileId { get; set; }

    [StringLength(50)]
    public string OriginalFileName { get; set; }

    [StringLength(100)]
    public string Name { get; set; }

    [StringLength(5)]
    public string FileExt { get; set; }

    public int Height { get; set; }
    public int Width { get; set; }
    public long SizeInBytes { get; set; }
    public DateTime DateCreated { get; set; }

    public CloudFile()
    {
        this.DateCreated = DateTime.Now;
    }
}

My Creative Class

public class Creative
{
    [Key]
    public int CreativeId { get; set; }

    [Required]
    public int OfferId { get; set; }
    public virtual Offer Offer { get; set; }

    public virtual CloudFile CloudFile { get; set; }

    [StringLength(100)]
    public string Alt { get; set; }

    public DateTime DateCreated { get; set; }

    public Creative()
    {
        this.DateCreated = DateTime.Now;
        this.CloudFile = new CloudFile();
    }
}

My Merchant Class

public class Merchant
{
    #region Keys
    [Key]
    [Display(Name = "Merchant ID")]
    public int MerchantId { get; set; }
    #endregion

    [Required]
    [Display(Name = "Merchant Name")]
    [StringLength(256)]
    public string Name { get; set; }

    public virtual CloudFile CloudFile { get; set; }

    public ICollection<Offer> Offers { get; set; }
    public ICollection<MerchantLocation> Locations { get; set; }

    public Merchant()
    {
        this.Offers = new List<Offer>();
        this.Locations = new List<MerchantLocation>();
    }

I am not sure how to associate and save these objects properly in the database. I have tried adding a new CloudFile object to Merchant.CloudFile and then running the following:

    ......
    merchant.CloudFile = new CloudFile() {...set properties here...};
    MerchantDB.Modify(merchant);
    ......

    public static bool Modify(Merchant merchant)
    {
        using (AppDbContext db = new AppDbContext())
        {
            db.Entry(merchant).State = EntityState.Modified;

            //Return true if only 1 record was modified.  If not, return false.
            return (db.SaveChanges() == 1);
        }
    }

But it does not save the CloudFile and associate it with Merchant. I am able to directly save the CloudFile to the CloudFile table but there is still no association.

Thanks for you assistance in advance!

Answer 1

That is because you had not mentioned two way relationship , ie no navigation property from your cloudtfile to creative and merchant class , try adding below lines to your cloudfile model

public Creative creativeObj { get; set; }
public Merchant merchantObj { get; set; }

also change

db.Entry(merchant).State = EntityState.Modified; 

to

db.Entry(cloudfile).State = EntityState.Modified;