I need to alter/add my own custom behaviour to this dialogue box so that it points at my own 'file repository'.Building a Media File Provider is a nice and clean way to get this. You can then "inject" your own folder/file structure into the existing structure and thus get your files to show up nicely in dialogs etc. Your files will be 1st class citizens in Composite C1 and show up / work everywhere.
A Media File Provider in Composite C1 is a plug-in that implements Composite.Data.Plugins.DataProvider.IDataProvider and can serve Composite.Data.Types.IMediaFile data. That statement probably made little sense, so take a look at the namespace Composite.Plugins.Data.DataProviders.MediaFileProvider in our source code and especially the MediaFileProvider class.
For a general introduction to writing data providers for Composite C1 see http://docs.composite.net/Data/CustomDataProviders
There is also a custom media file provider at https://compositec1contrib.codeplex.com/SourceControl/latest (DataProviders.FacebookMediaProvider).
Marcus