Joining three tables using linq

Question

I have three tables as:

 public class Description
    {
        public int DescriptionID { get; set; }

        // Attributes 

        public virtual List<Image> Image { get; set; }     

    }

public class Image
    {
        public int ImageID { get; set; }

        // Attributes       

        [Required]
        public int DescriptionID { get; set; }

        [ForeignKey("DescriptionID")]
        public virtual Description Description { get; set; }

        public virtual List<ImageSection> ImageSection { get; set; }
    }



public class ImageSection
    {
        public int ImageSectionID { get; set; }

        // Attributes

        public int? ImageID { get; set; }

        [ForeignKey("ImageID")]
        public virtual Image Image { get; set; }

     }

I have DescriptionID . What will be the linq to get all the ImageSection s having that DescriptionID ?

Answer 1

var result = dbContext.Images.Include(i => i.ImageSections)
                 .Where(j => j.DescriptionID == 1)
                 .SelectMany(im => im.ImageSections).ToList(); 

I hope this will help

Answer 2

This should do the trick

var descriptions = new List<Description>();

            var descriptionId = 1;

            var result =
                descriptions.Where(d => d.DescriptionID == descriptionId).SelectMany(
                    im => im.Image.SelectMany(ims=> ims.ImageSection));

Answer 3

It seems like you do not need to join three tables given the description of your problem. As you already have the DescriptionID that you want to join on you can ignore the Description table.

Try this:

var query1 =
    from i in db.Images
    where i.DescriptionID == descriptionID
    join s in db.ImageSections on i.ImageID equals s.ImageID
    select s;

However, since your table definitions already contain the child collections you could do a basic SelectMany without worrying about joins per se.

Try this as an alternative:

var query2 =
    from d in db.Descriptions
    where d.DescriptionID == descriptionID
    from i in d.Image
    from s in i.ImageSection
    select s;