Things to remember while designing VSTO 2005 solutions

Programmatic Limitations of Host Controls

• For each host item and host
  control there is an underlying native Word or Excel object which can be
  accessed via the InnerObject property of the host item or host
  control. You cannot however, cast a native object to it’s host
  item or host control.
• Host items are not created
  automatically when you create a new document or worksheet at
  runtime. For example, if you add a Word document at run time, it
  will be of the type Microsoft.Office.Interop.Word.Document rather than
  Microsoft.Office.Tools.Word.Document.
• Host controls and Windows
  Forms controls cannot be added to a native Word document or Excel
  worksheet, they can only be added to a host item.
• Most methods and properties of
  host items return the underlying native Office object upon which the item
  is based
• VSTO does not provide
  individual collections for each type of host control. For example,
  it is not possible to enumerate each Microsoft.Office.Tools.Word.Bookmark
  control in the document using the Microsoft.Office.Interop.Word.Bookmarks
  collection. You can use the ControlCollection to iterate through all
  controls (host controls and Windows Forms controls) on the document and
  then look for items that match the type of host control that you are
  interested in
• In Microsoft Word, you can
  pass a host control to a method or property that requires a native Word
  object for which there is a corresponding host control. However, in
  Excel, you must pass the native Office object rather than the
  corresponding host control. You can use the InnerObject property of
  the host control to pass the native Office object
• If a user deletes or cuts a
  control from the document at run time, the control cannot be restored by
  using the Undo or Paste methods. The Undo and Paste operations will
  add the underlying native Office object back to the document, but the
  object is no longer a host control.

Managed Windows Forms Controls

• Controls can be added either
  manually or programmatically
• Controls can be added to a
  Windows form, the actions pane, or directly on the document.
• Windows Forms controls are not
  supported inside of a header or footer, or within a subdocument.

The following controls and components are
not available in the Toolbox and are not supported for use on documents in VSTO
2005:

• BindingNavigator
• ContextMenuStrip
• CrystalReportViewer
• DataGrid
• DirectoryEntry
• DirectorySearcher
• ErrorProvider
• EventLog
• FileSystemWatcher
• FlowLayoutPanel
• GroupBox
• MainMenu
• MenuStrip
• MessageQueue
• NotifyIcon
• PageSetupDialog
• Panel
• PerformanceCounter
• PrintDialog
• PrintDocument
• PrintPreviewControl
• Process
• RichTextBox
• SerialPort
• ServiceController
• SplitContainer
• Splitter
• StatusBar
• StatusStrip
• TabControl
• TableLayoutPanel
• System.Timers.Timer
• System.Windows.Forms.Timer
• ToolBar
• ToolStrip
• ToolStripContainer
• ToolStripDropDown
• ToolStripDropDownMenu
• ToolStripPanel

Unsupported methods and properties of Word
controls

• Hide
• Show
• Anchor
• Dock
• Location
• TabIndex
• TabStop
• TopLevelControl
• Visible

Unsupported methods and properties of
Excel controls

• Anchor
• Dock
• Location
• TabIndex
• TabStop
• TopLevelControl