I have a winform in witch I have a custom LongPanel with textboxes.
In order to validate an eventually edited textbox when the user click somewhere out of textBoxY I use the following code:

  Private Sub LongPanel_MouseClick(ByVal sender As Object, _
                                   ByVal e As MouseEventArgs) _
                                         Handles MyBase.MouseClick
      _AttachedPanel.Select()
  End Sub

In runtime application freezes at the "Select" line... I receive infinite panel Leave events(sender is a panel)... any idea why?

EDIT:

precision on panels parents:

Form => SplitPanel => _AttachedPanel | _LongPanel
(_LongPanel contains a reference to _AttachedPanel)