How to hide/show the tool window but not close it

I have a VS2010 Isolated Shell application and I have a tool window as below

publicclassMyWindow:ToolWindowPane

And this tool window supports multiple instance

[ProvideToolWindow(typeof(MyWindow),MultiInstances=true,Style=VsDockStyle.MDI,Transient=true)]publicsealedclassMyVsxPackage:Package

Then in my application I can open more than one tool window (each tool window has its own window Id), but when I close one of them I just want to hide it, and next time when I reopen the window the settings on the window should keep the same before it was closed, how to handle this?

In another words, my question is: is there any way that prevent the multiple instance tool window from being closed by click the 'x' button (just hide it)?

Thanks in advance!