Question

I’m having trouble understanding how to create relationships between classes on a project that I’m building.

I have a class Photo that has a required one-to-one relationship with PhotoExif, and Photo has an optional one-to-one relationship with FeaturedPhoto.

I’m getting the error:

Unable to determine composite primary key ordering for type Website.Models.PhotoExif. Use the ColumnAttribute or the HasKey method to specify an order for composite primary keys.

Help would be much appreciated.

Photo.cs

public class Photo
{
    [Key]
    public int PhotoID { get; set; }

    public string Title { get; set; }

    public string Description { get; set; }
    public Orientation Orientation { get; set; }
    public int Rating { get; set; }
    public string URL { get; set; }
    public string Filename { get; set; }
    public DateTime DateAdded { get; set; }
    public bool Hide { get; set; }
    public string MetaDescription { get; set; }
    public string MetaKeywords { get; set; }

    public virtual PhotoExif PhotoExif { get; set; }
} 

PhotoExif.cs

public class PhotoExif
{
    [Key]
    public int PhotoExifID { get; set; }

    public int PhotoID { get; set; }

    public string ShutterSpeed { get; set; }
    public string Aperture { get; set; }
    public string FocalLength { get; set; }
    public int ISO { get; set; }
    public string ExposureBias { get; set; }
    public bool Flash { get; set; }
    public string WhiteBalance { get; set; }
    public string Lens { get; set; }
    public DateTime DateTaken { get; set; }
    public float Longitude { get; set; }
    public float Latitude { get; set; }
    public int Zoom { get; set; }
    public string Location { get; set; }

    public virtual Photo Photo { get; set; }
}

FeaturedPhoto.cs

public class FeaturedPhoto
{
    [Key]
    public int FeaturedPhotoID { get; set; }

    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
    public string InformationLocation { get; set; }
    public string ImagePosition { get; set; }

    public virtual Photo Photo { get; set; }
}

Answer 1

As per the error message:

Use the ColumnAttribute or the HasKey method to specify an order for
composite primary keys.

you need to add [Column(Order=”#”)] annotations to PhotoID and PhotoExifID properties of the PhotoExif table.