TreeView Basic Operation

Hello Salavatore, Hello Derek (How are you ?)
To illustrate what Derek rightly says about using a TreeView in MVD, here is an example of what you get with a TV.
I admit that the one used by MVD is not great in my opinion, I would have preferred a TV like in Delphi7 much simpler to implement.
To illustrate what Derek describes, in my application on the management of a database on birds responding to a command, the choice of a family in the initial TV displays the different birds belonging to this family and a click on the name of a bird calls the form describing it (with photo and song, or even video when it exists).
At first, I had trouble understanding the philosophy of MVD's TV.
After many emails with Dmitri, I managed to master it, but it took time.
Hang in there if you want to get there, don't forget to allow users to create parents and children, you can also automatically sort alphabetically without using Up and Down buttons (like I did at the beginning - it's a pain!)
Good luck and if you need anything, come back to us, you will have all the necessary information.
JB

Hi Salvatore, Salut Jean (oui, tout va bien ici, merci.  Et chez toi ?),
In my previous example, the foreign key setting was left over from your original attachment - it didn't need to be there.  Instead, it should be set as per 'screenshot1' in the attachment.
To clarify, there are three things that you need to set correctly.
1.  In the data schema, the table that contains your treeview structure must have a field called 'parentid' (defined as integer).   
2.  The 'foreign key' in the 'treeview' settings screen can simply be the name of the table that holds the structure of your treeview (the 'foreign key' label is perhaps a bit misleading).  You can simply type in the name of the table manually. 
3.  Select 'parentid' in the 'parent id field (see 'screenshot1').
There is no requirement for a separate 'childrens table' - that is the whole point of using a 'treeview';  all of the 'child' records are held in the same table as their 'parent' and they are linked back to their relevant parent by the 'parentid' field. 
Have a look at 'screenshot2' in the attachment which hopefully clarifies this;  this is a view of the raw data (using SQLiteStudio) which shows, for example, that the entry 'Hollywood' has an ID of 19.  All of the records that are 'children' of 'Hollywood' have their own IDs BUT HAVE A PARENTID OF 19 - this is how the relationship is automatically maintained.
IF YOU WERE USING TABLEGRIDS, then you would have TWO TABLES (eg 'groups' and 'members' with a foreign key maintaining the relationship between them).  But with 'treeviews' all of the informaiton is held in A SINGLE TABLE with the relationship being maintained instead by a 'parentid';  this is the fundamental difference.
Derek.