In order to use the AnnotateViewer.MouseTool, the AnnotateViewer.Annotations.InteractMode needs to be set to AnnotateInteractMode.None while a mouse tool is being used.
When you are switching to a MouseTool, set the InteractMode to None before changing the MouseTool. When you are finished with the tool, set to MouseTool to None before switching the InteractMode back to Author.
The reason for this is because the mouse tools will steal some event messages from AnnotateViewer, causing possible exceptions to occur.
Original Article:
Q10075 - INFO: How can I use the MouseTools with DotImage AnnotateViewer?