The application that I'm working on, has a main customized WPF window.
There is a control that lies inside this main window (a plotting graph) that is drawn in a canvas. Now the problem is, I want to implement a window like approach to this canvas ( a titlebar + Close button + moving inside the main window + resizing it). How should I approach this?
Problem is, if I design the control as a separate window, it won't be associated with my application (in a UI sense).
What i think is drawing a titlebar in the canvas and mimicing it with the windows titlebar functionality. But i don't know whether there is any better approach.
What it sounds like you want to do is to write a traditional MDI application ("Multiple Document Interface") using WPF:
This style of application design is not that common today as it used to be back in the Windows Forms days. There are many arguments both for and against it but if you are certain this is what you want, then there is a WPF library on codeplex that handles this:
There is also a discussion over at the UX stackexchange about alternatives to MDI layout which you may find interesting.