Etienne is on fire with his recent blog posts about SubSonic, so I thought I would contribute one too.
Five months ago I submitted a patch to SubSonic concerning their ManyManyList control (SubSonic.Controls.ManyManyList). I love the control as it is a real time saver, but there are a few limitations.
1 - Cannot use a view as a primary table or foreign table.
In my context, I want to display strings and these strings are not directly in the ForeignTable. The control had assumptions on the presence of a primary key.
2 - Cannot sort the resulting elements
In my context, I want to sort the strings alphabetically.
3 - Cannot filter the foreign table
In my context, a particular item can be in multiple categories, but the set of categories it can be in is not the full foreign table.
4 - The save mechanism deletes all rows and recreates them. If you have other columns in your map table, you lose all that information. Furthermore, there are no checks to see if the delete/recreation is necessary. Even if there are no changes, it still deletes/recreates everything.
I've pretty much re-written everything to support the listed behaviour. The parameter names should be reviewed because they are not very user friendly, and I am not well versed in the SubSonic naming conventions. Since then, we've used this code in production and it appears to work perfectly for our purposes (and it should work exactly as the other one did out of the box if you don't specify any of the new properties).
Agrinei enhanced my code to make it even more customizable.
Download the patch directly on CodePlex and don't forget to vote for the issue!