Invalid keys in a TreeView Control

Each node of a TreeView has a key. The key is a string and must be unique [2].
Accidentally I discovered some unacceptable values for this key [3].

Generally, are rejected values that resembles a number:
- Integer literals, like '1'
- Integer literals followed by a period, like '1.'
- Integer literals preceded or folowed by a symbol sign, like '+1' or '1-'
- Numbers with commas between its digits, like '1,' ; '1,1,1' ; '1.,' or '.1,'
- Integer literals preceded or folowed by Space, Tabe or CR

Please try following example.

PUBLIC ofrm

ofrm=CREATEOBJECT("MyForm")

ofrm.show()

DEFINE CLASS MyForm as Form

      autocenter = .T.

      ADD OBJECT teeview as olecontrol WITH oleclass = 'COMCtl.treectrl', width = 300,height = 350

      PROCEDURE init

            LOCAL lcRoot,loRoot

            lcRoot='Root'

            loRoot = thisform.TeeView.Nodes.Add(, 1, m.lcRoot,'Root node')

            loRoot.Expanded = .T.

            * Rejected

            thisform.AddNode(m.lcRoot,'1')

            thisform.AddNode(m.lcRoot,'1.')

            thisform.AddNode(m.lcRoot,'1,')

            thisform.AddNode(m.lcRoot,'+1')

            thisform.AddNode(m.lcRoot,'1.,')

            thisform.AddNode(m.lcRoot,'.1,')

            thisform.AddNode(m.lcRoot,'-1')

            thisform.AddNode(m.lcRoot,'1+')

            thisform.AddNode(m.lcRoot,'1-')

            thisform.AddNode(m.lcRoot,' 1')

            thisform.AddNode(m.lcRoot,'1 ')

            thisform.AddNode(m.lcRoot,CHR(13) + '1')

            thisform.AddNode(m.lcRoot,CHR(9) + '1')

            thisform.AddNode(m.lcRoot,'1,1,1,1')

           

            * Accepted

            thisform.AddNode(m.lcRoot,CHR(13))

            thisform.AddNode(m.lcRoot,CHR(9))

            thisform.AddNode(m.lcRoot,'1 1')

            thisform.AddNode(m.lcRoot,'1E')

            thisform.AddNode(m.lcRoot,'1+1')

      ENDPROC

      PROCEDURE AddNode

            LPARAMETERS lcRoot, lcKey

            LOCAL loErr as Exception

            TRY

                  thisform.TeeView.Nodes.Add(m.lcRoot, 4, m.lcKey,m.lcKey)

            CATCH TO loErr

                  ACTIVATE SCREEN

                  ? m.lcKey, loErr.ErrorNo , loErr.Message

            ENDTRY

      ENDPROC

ENDDEFINE


Bibliography
[1] TreeView Control
[2] Key Property
[3] The code the lead me to these conclusions

Related posts
http://praisachion.blogspot.com/2017/09/correlation-between-margin-and-fontsize.html
http://praisachion.blogspot.com/2017/08/invalid-keys-in-treeview-control.html