Our application uses a XML configuation file. I thought that it would be nice to distribute some XML editor with our application, so that the user can conveniently edit the config file. Features should be:
Does anyone know of such an editor?
Notepad++ (free as in beer and as in free speech) http://notepad-plus.sourceforge.net/uk/site.htm
This fulfills most of your requirements; however, it only has tag collapsing and will not show validation errors or auto completion.
XML Notepad by MSFT is good, but it does not allow wide distribution. You may be able to get by checking installed apps for XML Notepad and, if it's installed, sending startup arguments to the app.