I hate it when the IDE is psychic

[Barfy the Wonder Camel]

OK, here it is. I wanted to add a DateTimePicker column to the
DataGridView at design time, which means it would be available as a
column type when laying out a dgv. I got some source code from
http://forums.microsoft.com/msdn/ShowPost.aspx?siteid=1&PostID=66954
which seems to work -- the new column type is indeed showing up in the
designer. What's screwing with my head is that I can't see how just
adding this code to a separate dll automagically adds it to the IDE
designer. Is it just a matter of the new column being a descendant of
DataGridViewColumn? There *is* some hint in the aforementioned thread
that the IDE goes out exploring for something to add to the
collection, but it's not really clear. I might try removing the
subclassing to see what happens, but right now I'm kind of scared to
touch anything, since it seems to be working. Any ideas?

 

[Barfy the Wonder Camel]

Of course as usual the microsoft sample only shows the very basics.
Does anyone know how to persist values in a custom datagridview
column?