How is your 'uc' variable declared because this:will only return a Control reference. If you've declared 'uc' as type Control then you won't get Intellisense because the Control class doesn't have a TextProperty property. If you have declared 'uc' as the correct type then you must have Option Strict turned Off or this:wouldn't compile.
I'd rather see safer code like this:
vb.net Code:
For Each page As TabPage In Me.tbcTasks.TabPages
For Each ctl As Control In page.Controls
If TypeOf ctl Is MyUserControl Then
MessageBox.Show(DirectCast(ctl, MyUserControl).TextProperty)
Exit For
End If
Next ctl
Next page