We have an ASP.NET web-application which has become difficult to maintain, and I'm looking for ideas on how to redesign it. It's an employee administration system which can be highly customized for each of our customers. Let me explain how it works now:

On the default page we have a menu where a user can select a task, such as Create Employee or View Timesheet. I'll use Create Employee as an example.

When a user selects Create Employee from the menu, an ASPX page is loaded which contains a dynamically loaded usercontrol for the selected menuitem, e.g. for Create Employee this would be AddEmployee.ascx

If the user clicks Save on the control, it navigates to the default page. Some menuitems involve multiple steps, so if the user clicks Next on a multi-step flow then it will navigate to the next page in the flow, and so on until it reaches the final step, where clicking Save navigates to the default page.

Some customers may require an extra step in the Create Employee flow (e.g. SecurityClearance.ascx) but others may not.

Different customers may use the same ASCX usercontrol, so in the AddEmployee.OnInit we can customize the fields for that customer, i.e. making certain fields hidden or readonly or mandatory.

The following things are customizable per customer:

• Menu items
• Steps in each flow (ascx control names)
• Hidden fields in each ascx
• Mandatory fields in each ascx
• Rules relating to each ascx, which allows certain logic to be used in the code for that customer

The customizations are held in a huge XML file per customer, which could be 7500 lines long.

Is there any framework or rules-engine that we could use to customize our application in this way? How do other applications manage customizations per customer?