Often I need to explore an issue around using C# with the Visio COM automation classes. Invariably, I rebuild the same initial project each time and go through the same basic steps of having to remember exactly how to use Document.OpenEx to load a stencil.
To save myself, and you that time, I created a simple starter C# project. It builds a command line app that should get you started. The EXE simply starts Visio 2010, creates a new doc, loads the “basic” stencil, then draws a rectangle, and finally drops the “rounded rectangle master”.
You can get a ZIP file of the Visual Studio 2012 project on my SkyDrive.