Migrate a Desktop legacy accounting application from desktop to Web, How/Approach/Patterns?

I have a need to migrate a legacy, desktop based, single user, accounting application to a web based, with rich UI(possibly), multi user one. It is more or less re-writing the entire legacy system.

And that too as QUICKLY as possible.

Can somebody make any suggestions on architecture and some pointers on preferable approach or patterns, etc? For the database end, I have already decided to use Entity framework with a tracking开发者_StackOverflow社区 Repository pattern around it.

I have ASP.NET MVC in consideration. But not sure that down the line, I decide to replace the UI with Silverlight, this will be possible with ASP.NET MVC? I know with MVP it is a little bit easier?

Don't want to start with Silverlight already as it takes a lot of time to design UI and use MVVM + WCF RIA, the development moves at a snail's pace!

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We did a similar migration for a desktop app but it was not quick, however it was also a large enterprise system.

1. We totally decoupled the business layer from the presentation this was mostly done already but there were a few layer violations we had to solve. Re-deployed the old app with the new seperations

2. wraped the Business layer in a WCF web service and moved our reporting to a new website old app redirected users to the website.

3. Moved UI to the website running in parallel with the old app all new installations were web only.

4. Replaced the Desktop app for all users.

While this process is not quick it did work for us. the project was also a very large client server application so we favored caution over rapidity.