Hi Arno,
DockingManager extended property will be enabled for a control, only if the control is hosted in a Form/UserControl which contains the DockingManager instance. So if you want to dock a control inside the
ToolStripContainer, you have to add a control and docking manager an UserControl and the Usercontrol should be added into the ToolStripContainer.
I have created a sample which illustrates the above functionality. Please take a look at the sample and let me know if you have any other questions.
Regards,
Vijay
WindowsApplication2.zip