Question

I have a folder hierarchy where a folder can have a parent folder, with unlimited depth.

So…
Folder A
FolderId = 1
ParentFolderId = Null (Top Level)

Folder B
FolderId = 2
ParentFolderId = 1 (Nested under A)

Folder C
FolderId = 3
ParentFolderId = 2 (Nested under B)

Folder D
FolderId = 4
ParentFolderId = 3 (Nested under C)

I want to get all of the children of Folder B (or whatever folder the user has selected) so that I can delete all of the children, but leave the parents (unless, of course, the top level folder is selected).

This is probably some fairly straightforward recursion or a foreach loop, but I’m struggling with it this morning! I’m using C# and EF, so something using that would be most helpful. I’d like the result as a flat list, if possible.

Ideally, I’d like to have it as a method off my custom Folder object so that any folder I have, I can just say Folder.Children() or something like that.

Folder Object:

  public class Folder
  {
    public int Id { get; set; }

    public string Name { get; set; }
    public string Description { get; set; }

    public int? ParentId { get; set; }
    public virtual Folder Parent { get; set; }

    public virtual ICollection<File> Files { get; set; }
  }

Thank you in advance.

Answer 1

Here is a recursive method which will do what you want. You call this method with a argument of Id of folder which child you want to get and it will retrive all child and childs-of-childs and so-so-so.

public List<Folder> GetFolderChildsRecursive(Int32 forlderId)
{
    List<Folder> childsOfFolder = context.Folder.Where(e=>e.ParentId == folderId).ToList();
    foreach(Folder child in childsOfFolder)
    {
        List<Folder> childs = GetFoldersRecursive(child.Id);
        childsOfFolder.AddRange(childs);
    }
    return childOfFolder;
}