News just in, the lasted version of Excel DNA (0.27) has been released by Govert, and can be had here.

From the site:

Release Notes

This release adds support for the .NET Framework version 4: add a RuntimeVersion=”v4.0″ attribute to the DnaLibrary tag to load the .NET 4 runtime.

Additional changes:

• XML-based hierarchical CommandBars updated (thanks to Bertrand).
• Shadow copy support: add ShadowCopyFiles=”true” to the DnaLibrary tag.

This might inspire a change to C#!