Why would you think that your Forms code could work in WPF? These libraries are very different.
You need to do something like this:
Dim myUserControl As New MyUserControl
myDockPanel.Children.Add(myUserControl)
DockPanel.SetDock(myUserControl, Dock.Bottom)
By the way, avoid those names:
obj1
,
UserControl1
. Names should be semantic; no numbers in names; in general, observer good Microsoft naming conventions.
—SA