Why does Windows explorer open multiple instances of Matlab2013a when I am using DDE-commands?

Question

Windows explorer uses DDE to communicate with applications for things like file-opening. These DDE-commands can be set in the "folder options" of Windows explorer. Matlab has an undocumented DDE-interface, which I use for telling Matlab to analyze any file I double-click in Explorer.

I recently upgraded from Matlab2011a to Matlab2013a. In folder options, I updated the path in the "Application Used to Perform this Action" field to point to the new Matlab binary. For all my previous upgrades this was enough to make it work. But now, instead of analyzing the file in the instance of Matlab that is already running, a new Matlab instance is opened for every file!

What is causing this error?

Answer 1

Because Matlab's DDE-interface is undocumented, Mathworks feels free (and has every right) to change the DDE-behaviour between versions. In Matlab2013a they changed the DDE "Application Name" so that it now includes the version of Matlab. In this case, the correct "Application Name" is ShellVerbs.Matlab.8.1.0.

For reference, here is a screenshot of the settings (sorry, my Windows XP is in German.)