 <p><a href="http://bplusdotnet.sourceforge.net/" rel="nofollow">http://bplusdotnet.sourceforge.net/</a> but this one is known to be somewhat buggy on deletes.</p> <p>Another one that appears to work well:</p> <p><a href="http://www.codeproject.com/KB/database/RaptorDB.aspx" rel="nofollow">http://www.codeproject.com/KB/database/RaptorDB.aspx</a></p> <p>RaptorDB allows you to store key/values either indexed using a b+ tree or a hash index. You can pick when you create the files.</p>