In an SDI (single document interface) application, the DockHost is the control in which the Tool Windows can be docked, while the ClientHost, which must be a child of the dock-host and is optional, is the control around which tool windows can be docked (work area). The client-host will always be docked in the dock-host and will occupy the space not occupied by tool windows. This means that if no tool windows are contained in the dock-host, the client-host will occupy all of the space in the dock-host.
In an MDI (multiple document interface) application, the client-host will always be the MDI client (where the MDI children are located) of the MDI container (dock-host). Any control assigned as the client-host will be ignored. Any controls that are docked (in the Windows-Forms sense) to the left, top, right, or bottom of the dock-host will be excluded from the client area (MDI client).
As of version 2.0 of Xceed Docking Windows for WinForms, tool windows that have an Mdi state can now be displayed as tabbed documents through the use of a tabbed-MDI manager. For more information, refer to the MDI Tool Windows or Tabbed-MDI Manager topics.