Providing SaaS functionality to a .NET portal with DLLs

I'm not sure I'm asking the right question here, but I'm looking to provide web based functionality from one ASP.NET application to another remote 'portal-like' application. Is it possible to simply give the portal a DLL? As an example, let's say the SaaS web app has a patient-entry form that I want to be able to use from the portal application. I would like the portal app to be able to set preferences (permissions, color, style, etc), make a function call, and have that capability presented within a certain div or something. Is there any .NET technologies that provide this kind of integration?

EDIT:

Here is a link to a quick diagram I made trying to describe the scenario: http://img.ly/ESG. I know there are other ways of doing this (eg JSON-P calls), but I need to give the portal developers something they can control on their end. Also, if anything changes 开发者_StackOverflowthey'll know I will send them a new version of the DLL which will indicate to them the new functionality.

I'll give you a shopping list of things to check out:

1. DotNetNuke: http://www.dotnetnuke.com/
2. Workflow Foundation - http://msdn.microsoft.com/en-us/netframework/aa663328.aspx
3. Microsoft SAAS platform - http://www.microsoft.com/serviceproviders/saas/default.mspx

Depending on exactly what you're looking for, you might also research "multitenancy".

To answer your original question, yes, you can do it with DLL's, but there are easier ways to do it.