db4o
Embed db4o's native Java and .NET open source object database engine into your products and store complex object structures with ease. db4o provides superior performance and is simple to install. Download a free version of db4o under the GPL license and start your evaluation now!

Visual FoxPro Toolkit for .NET
Class library with over 225 Visual FoxPro functions for use with any .NET language. The included VFPToolkitNET.DLL is a .NET managed code DLL (not a COM wrapper) and does not require Visual FoxPro. The functions supported execute fast since they are all written in .NET and compiled into a managed code .NET DLL.