Vfrdtyky

The objective is to make a Linq query to the database that gets the rest of ids that link back the input id in the method called GetFolder

Sample Data

Id              parentId

10              9

11              10

12              10

13              12

14              13

15              13

100             20



Expected Output

Id              parentId

10              11

12              10

13              12

14              13



  public class Folder 

  {

    [Key]

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

    public int Id { get; set; }



    [Column("Parent_Id")]

    public int? ParentId { get; set; }



    public virtual ICollection<Folder> Children { get; set; }

  }

Have the ICollection allows me to go one view the siblings of that folder.
GetFolders methods return these:

Id              parentId

10              11

11              10

12              10



    private async Task<Folder> GetFolder(int folderId)

    {

      var entity = await Database.Folders

        .Where(e => e.Id == folderId)

        .Include(e => e.Children)

        .SingleOrDefaultAsync();



      return entity;

    }

I tried to write a recursive function to get the rest of the Ids but it doesn't work correctly.
Does anyone have any recommends on how to write this recursive function to receive the rest of the Ids.

How about

IEnumerable<int> GetRelatedIds(Folder root)

{        

    var ids = root.Children.SelectMany(c => GetRelatedIds(c)).ToList();

    ids.Add(root.Id);



    return ids;

}

This will also include the Id of the root folder. If you don't need it you can either just remove it from the list (it will be the last element), or run this method for all children of the root and concatenate the results.