Embeddable 3D Viewer for Visual Studio project

Question

Hi,

I'm looking for some 3D viewer software that I can embed into a Visual Studio 2010 project and I was wondering if someone could give me a recommendation.  My needs are:

1. Embeddable as dll in a Visual Studio 2010 project
2. Common 3D Viewer features (pan, zoom, rotate, change view, change color, pickable entities, etc.)
3. Takes VRML, IGES, or STEP
4. Programmable API in a .NET language (VB or C#)
5. Works with both Windows XP or Windows 7 (as opposed to older ActiveX technology)
6. Free download, open source preferable

Thanks