Building solutions

I was not sure where to post this question, hope this is the right place.

I am building a new VB.Net & ASP.Net web application that has many modules. I want to build these in a way that one can be brought down without having to bring down the whole system if we need to do an update. I want to know what is the best design for my projects. Here is an example of what I am asking

Lets say we are creating a sales tracking app.....

Project one will be the ADMIN side where all administrative actions are done by the system administrator IE building the base system tables.

Project two will be the sales entry module where someone will hand key in all the sales tickets into the database.

Project three will be a on-line lookup of sales reports.

Now, with those threee projects, in .NET, is it better to have them all under the same solution as different projects?

OR seperate solutions?

OR one solution one project broken down at the folder level?

All of these will interact in some way with each other, so they need the ability to forward to each other when requested.

Any suggestions would be appreciated.... Thanks!

I think it would depend on how many people are going to be working on each part, if any of the parts can be reused, and if you are separating your classes and UIs - n-tier architecture. I commonly have my core classes in a separate dll and try to keep my UIs in the main exe. I also have several supporting dll (like for exception handling) that I also hook in that are reused for many of my different projects. So I favor separating things out, but I am sure there are varying opinions on this.

If they are seperate applications, then I would use seperate solutions. Where the applications intersect each other, I could create a seperate solution for that as well. You can then add a reference to the dll's as needed.

Keeping things seperated might help you better manage your applications, and has the benefit of making you think twice of how you are implementing features. This has the added benefit of likely making your design better overall.

Just my opinions.

A good place to start researching these architecture type questions is:
http://www.msdn.microsoft.com/architecture/