I am able to register the usercontrol as the toolwindow using the prism integration with the docking.
This usercontrol consist of some wpf controls and some winform controls.
Suppose the height of the winform control is 100 and height of the main usercontrol that contain this winform control and some wpf control is 150.
so as i dock this toolwindow containing the above usercontrol to the top position of the dockguide then a docking splitter will come with that toolwindow.
So as i resize(decrease the height of the toolwindow) of that toolwindow(consist of some winform controls and some wpf controls) using the docking splitter,then wpf controls will remain in that toolwindow but winform controls of that toolwindow will come out of that toolwindow as i decrease the size of the toolwindow from 100 that is size of the winform controls.