Does installing .NET 4.0 Framework replace the previous .NET versions?

I get this question all the time with developers asking if installing .NET 4.0 will replace the existing .NET 3.5 framework on their machine. The answer is NO.

.NET 4.0 framework does not replace or remove the previous .NET frameworks. .NET 4.0 successfully installs side-by-side with previous versions of .NET framework including .NET 3.5, 3.0 or even 2.0.

Also note that using Visual Studio 2010 IDE, you can target your applications to use the framework of your choice, i.e. you can use the same IDE to build .NET 2.0, 3.5 and 4.0 apps on the same machine. You just have to choose your desired framework when creating a new project, as shown below


About The Author

Suprotim Agarwal
Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

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Anonymous said...

Thanks for this! It really helped.

Russell said...

So 4.0 can co-exist with 3.5 but is 3.5 a requirement?

I'm fairly sure that 4.0 does not contain everything that 3.5 does. If that's the case then what happens if I develop an application in which I want to use some functionality from 4.0 and some from 3.5?

Would I then require both 3.5 and 4.0 be installed?

I'm actually trying to figure out which version of .NET my users have installed so that I know what functionality I can use but that difficult if I have to report every single version.

Anonymous said...

I think the best wording that needs to be documented is:
"If you install .NET 4.0, does it include functionality for 1.0, 2.0, 2.5, 3.0, and 3.5 OR do you need to install the previous versions to receive functionality introduced in "

Anonymous said...

What about framework 1.1 ?

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