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i have few applications running on dot net framework 2.0 and 3.5. Now i want to install dot net frame work 4.0 on same server but i m afraid this could crash the running application.m i correct dot net 4.0 will work with these 2.0 & 3.5 without any issue?
please suggest me


no i do not want to recompile my previous application. i want to install new framework at server and new application which build in .Net 4.0 will run without crashing previous version(2.0 and 3.5).
Updated 26-Feb-11 6:49am


.Net 4 is backward compatible with the previous versions of .net.

It means that is you want to recompile an application that was designed using a previous version of .Net and target the new .Net4 framework it will work.

See here for details:[^]

In another hand .Net2, 3, 3.5 and 4 can happily coexist on the same PC and each application will use the version of .Net it is targeting.

So basically your issue is not an issue at all.

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Monjurul Habib 26-Feb-11 18:45pm    
That would be my answer too,this is the only reason I vote 5 :-)
It was designed such that this is not an issue.
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I think the following links will help you too:
Upgrade an ASP.NET Web Application to ASP.NET 4
Host Web Applications That Use Different Versions of the .NET Framework on the Same Server
Deploy Web Projects Targeted for Earlier Versions of the .NET Framework

If this would be really helpful to you then don't forgot to Vote and Make Answer as Accepted.
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I disagree - I have tried running 2 and 4 on same server in a production environment and it becomes unstable
Remove any website that uses 4 and it becomes stable again
So, in my opinion, it works in theory but not in practice
I have tried this on two different servers - both became unstable
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