Now that Visual Studio 2010 RC is released I was wondering if anyone knows what pros/cons there are to upgrading my existing ASP.NET applications to target the .NET 4 framework? (Apart from waiting until the Final release which should be even more stable)
At least, you must check if your webserver have support for ASP.NET 4.0 application pools.
If you are not going to rewrite some parts of the application to use new features in ASP.NET 4.0, I don't think there are many benefits. Unless they introduced performance optimizations for already existing functionality, but I don't think you would get those automatically without modifying code.
Otherwise there are plenty of goodies like URL Routing, SEO optimizations, ViewState performance, etc.
Pros: You will be ready when it is final
Cons: Be ready for quite a few issues, if you have the time.
Here is a list and overview of some of the issues people are encountering and some praises:
http://weblogs.asp.net/scottgu/archive/2010/02/08/vs-2010-net-4-release-candidate.aspx
And my favorite resource as it is impossible to give you a break down of Pros and Cons considering what may be a pro for me, may be a con for you and vice versa:
If you're going to be using C# for your development, then here is one big thing that the next version of the framework and C# will have; Dynamic Types:
From Scott Hanselman's blog:
C# 4 (not 4.0, the marketing folks say it's .NET 4, etc.) adds the dynamic keyword. I've explained this saying:
"There's no way for you or I to know the type of this now, compiler, so let's hope that the runtime figures it out."
The key point here, in bold, because it's significant is: having the type dynamic means “use my runtime type for binding”.
This is something quite different from the current version of C# and could have some pretty signifigant ways in which code is written. So hidden in all of the hoopla, the new framework does have some added value compared to the current frameworks.
Hope this helps some.
You have the go live license --> you can use all new asp features in production.
But you will have a few problems with VS.