.NET 4.0 and earlier versions

Question

.NET 3.5 was different and co-existed along with .NET 2.0. Is that still the same approach with .NET 4.0 or does it include functionality of previous versions of the framework rolled into it? In other words, if I have an app that uses .NET 2.0 functionality can I deploy .NET 4.0 and things will work or do I have to deploy both .NET 2.0 and 4.0?

Answer 1

At this point it is pure speculation about what .NET 4.0 on it's own will support with regards to assemblies compiled against previous versions of the CLR. MSIL has not changed but applications compiled against 4.0 reference 4.0 versions of the framework and CLR. Applications compiled against CLR 2.0 (including .NET 3.0 and .NET 3.5) execute against the 2.0 versions of the framework and CLR.

From ScottGu's blog:

"... .NET 4.0 has a new version number for both the framework libraries and CLR engine – which means it runs completely independently from .NET 2.0, 3.0 and 3.5. What this means is that you can install .NET 4.0 on a machine that has .NET 2.0/3.0/3.5 installed, and configure some applications to run using .NET 4.0 and others to run using the older .NET versions..."

Nowhere is this blog article is any confirmation about how .NET 2.0 compiled applications will interact with the 4.0 runtime, the only thing that is talked about is that Visual Studio 2010 will support multiple runtime Intellisense and compile to downlevel CLR versions.

Answer 2

.Net 4.0 will support previous framework also. you wont worry about deploying it into two frameworks .

Note : new framework is to add sugars to pervious versions :)

Read ScottGu's Blog

Answer 3

.NET 4.0 will be backwards compatible with previous versions of the framework. In addition, you'll be able to run processes using different versions of the CLR in the same application.