I looked at the test plugin NppPluginDemo, downloadable from
and then I made my own DLL based on that test plugin.
notepad++ was putting up a messagebox that the function messageProc was missing.
In other words, the test plugin needs to be updated to contain that function.
It would be nice with some plugin tutorial in addition to the samples. Only the messages was documented but nothing (as far as I can see) about the required functions in notepad++ plugins.
Indeed, NppPluginDemo.zip is not updated.
Download NppInsertPlugin.zip instead :