I want to create a list of Items with parent and children. I have already prepared the data in a sqlite file:

So I want to read this data (I can read data like var subjectnames = await db.SubjectNames.ToListAsync();) from the database and create a nested list based on being a parent and a child.Each item may have one or more children and the number is unknown.

this is my class:

public class SubjectName
{
    public int Id { get; set; }
    public long SubjectId { get; set; }
    public string Name { get; set; }
    public long ParentId { get; set; }
}

public class ExplorerItem : Observable
{
    public enum ExplorerItemType { Folder, File, CheckMark };
    public string Name { get; set; }
    public ExplorerItem Parent { get; set; }
    public ExplorerItemType Type { get; set; }

    private ObservableCollection<ExplorerItem> m_children;
    public ObservableCollection<ExplorerItem> Children
    {
        get
        {
            if (m_children == null)
            {
                m_children = new ObservableCollection<ExplorerItem>();
            }
            return m_children;
        }
        set
        {
            m_children = value;
        }
    }

    private bool m_isExpanded;
    public bool IsExpanded
    {
        get { return m_isExpanded; }
        set { Set(ref m_isExpanded, value); }
    }
}

and i have a ObservableCollection of ExplorerItem:

var list = new ObservableCollection<ExplorerItem>();

That all data must be added to it

Once the data is completed, the list should be displayed as follows in TreeView

The problem is that I dont Know how to create parent-child relationships and add them to the list. Because their number is not known and they include parent and child nested

CodePudding user response：

If using EF You can change the class and set the configuration as follows:

public class SubjectName
{
   public int Id { get; set; }
   public long SubjectId { get; set; }
   public string Name { get; set; }
   public long ParentId { get; set; }
   public SubjectName Parent { get; set; }
   public ICollection<SubjectName> Chidren{ get; set; }
}

public class SubjectNameConfig : IEntityTypeConfiguration<SubjectName>
{
    public void Configure(EntityTypeBuilder<SubjectName> builder)
    {
       builder.HasKey(e => e.SubjectId);

       // Relations
        builder.HasOne(d => d.Parent)
            .WithMany(p => p.Children)
            .HasForeignKey(d => d.ParentId)
            .HasPrincipalKey(d => d.SubjectId)
            .OnDelete(DeleteBehavior.Restrict);
    }
}