Question Regarding Plugin Architecture

[Joseph Ferris]

I am working on a Web Application that can dynamically load
UserControls, a la a plugin style system. When I create any new
controls within the project, all is fine.

What my question is, would be how might I be able to allow someone to
create a plugin that would not require that I rebuild the application -
or is it even possible? Right now, this is what I have:

A BasePage class that inherits from System.Web.UI.P age that is used to
extend the Page object for extended rendering functionality.

A BaseControl class that inherits from System.Web.UI.U serControl that
is used to extend the UserControl object for specific rendering
capabilities that are used by all plugins.

I have a page that inherits from BasePage. To it, I've added a
PlaceHolder control. Then on Page_Load, I simply use LoadControl to
load the specific control and add it to the PlaceHolder. My ultimate
goal would be to build up a repository of these objects in a database
so that I could configure certain controls to be used in certain
situations. Basically, it is a CMS-type application.

Like I mentioned, as long as the control exists in the main project,
all is well. But assume that a third party wants to develop a plugin.
I don't want to give access to the code to that person, for obvious
reasons.

Are my options limited to adding the DLL from the plugin to the /bin
folder of the main application? After I do that, how do I get the
application to recongize the DLL? If I put them in a subfolder
structure to keep them organized, does this impact anything in regards
to the ability to load the control?

Thank you, in advance, for any input.

Joseph

[Joseph Ferris]

I have made some progress. What I am doing now, instead of
LoadControl, is I am creating a reference to the Assembly by using
Assembly.LoadFr om(). I then cast it to the correct control type and
assign it to the control collection of a placeholder on the calling
page. This is what I have in my Page_Load on the ASPX page:

Dim MyPlaceHolder As PlaceHolder =
CType(Me.FindCo ntrol("Template Holder"), PlaceHolder)

If Not MyPlaceHolder Is Nothing Then

Dim DynamicASM As [Assembly]
DynamicASM =
DynamicASM.Load From(Server.Map Path("./New/bin/New.dll"))

Dim ControlInstance As MyLib.Page.Cont rols.Template =
CType(DynamicAS M.CreateInstanc e("New.Index" ),
MyLib.Page.Cont rols.Template)

MyPlaceHolder.C ontrols.Add(Con trolInstance)

ControlInstance .TestOutput()

End If

The TestOutput() method is defined in the base control instance, and
outputs "Base" to the screen when called, if it is not overriden. I
override it in the derived instance to display "Derived". When I run
the above code, it displays "Derived". But now, my new problem...

Any content in the derived control is not displayed. For example, I
added a table in the designer and recompiled. The instance I create
from the assembly is displaying "Derived", so it is creating it. The
events of the derived control are also being hit correctly, if I add
breakpoints in the debugger. I just can't get the table to show. I am
assuming that something is happening in LoadControl that this approach
does not do.

Does anyone have any idea as to might what be going on, or have a
better approach to this? I am feeling a little lost at the moment.
;-)

Thanks!

Joseph