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I have 4 Microsoft .NET Framework versions:

  • 1.1
  • 2.0 Service Pack 2
  • 3.0 Service Pack 2
  • 3.5 SP1

Do I need them all?

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Hopefully the answers can expand on the ideal order of installation (most likely lowest version up). –  Synetech Mar 3 '11 at 15:11
    
Added an answer...uninstall them all; install .NET 4 and you'll be fine. –  Aaron McIver Mar 3 '11 at 15:21
    
I know this question is old, but a Google search I just did brought me here. Read my comments to Aaron McIver's answer for the reason why Aaron's 'solution' will not always work. –  pepoluan Sep 6 '13 at 12:30
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5 Answers

There are 4 distinct versions of the .net framework.

  • .NET 1
  • .NET 1.1
  • .NET 2
  • .NET 4

All of those can be installed and uninstalled independently. This is where it starts to get interesting! .NET 3 was introduced (along with a service pack to .NET 2) and was an additional set of libraries to it. .NET 3.5 followed this trend (with a second service pack for .NET 2 and a service pack for .NET 3) and again required .NET 2 as it just extended it.

The latest release is entirely standalone and does not require previous versions. It is mostly backwards compatible so it is possible to get your old applications to work on it.

Whether you need any of them or not depends on what you're running. Most applications out there are still built for .NET 2 to 3.5 so installing 3.5 will cover you for that. I would recommend installing 4 as looking forwards that's what Microsoft want people to be using.

.NET 4.5 (and 4.5.1, 4.5.2) is an in-place update to .NET 4.

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-1 If you have .NET 4 you can run any app built with .NET 1.1+ –  Aaron McIver Mar 3 '11 at 15:20
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@Aaron its not a rule –  Shakehar Mar 3 '11 at 15:28
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.Net Framework 3.5 installation also installs all the previous versions from 2.0 and onward. Version 1.1 is an exception and has to be installed separately.

Since you seem to need the 3.5 SP1 version, this will also install all .Net versions from 2.0 and upwards. So you really have no choice about it, and attempting to uninstall one version may cause problems with the other versions that build upon it.

As there are very few products left that require .Net 1.1, one can wait with its installation until there is a real need for it. As it is not automatically installed, and if it is already installed, this means that it is required by some product that you have installed (unless you are on XP, where it is installed by default).

You have not mentioned .Net 4.0, but with this version Microsoft has tried to reduce the size of the software by not including all the previous versions. .Net 4.0 is therefore smaller, and is supposed to be backward-compatible with all previous versions from 1.1 and onwards. So in theory it is the only one you need.

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You're wrong about .NET 4 being built on top of 2. I've posted a more detailed answer below. Basically version 4 is the latest standalone version. –  Matthew Steeples Mar 3 '11 at 14:15
    
@Matthew Steeples: I fixed my answer not to include v4. I am not sure you are correct by implying that 2.0 is not installed by installing 3.5 SP1. –  harrymc Mar 3 '11 at 14:58
    
-1 If you have .NET 4 you can run any app built with .NET 1.1+ –  Aaron McIver Mar 3 '11 at 15:21
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@Aaron: Why down-vote? I say nothing about v4, since I have no experience with it. See the answer by Matthew Steeples for that. Down-voting too quickly is not good netiquette. –  harrymc Mar 3 '11 at 15:42
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@Aaron: Citing from your link : "However, in practice, this compatibility can be broken by seemingly inconsequential changes in the .NET Framework and changes in programming techniques". In any case, the same compatibility phrase was to be found as-is in the release notes of all .Net versions since 2.0, and it was never totally true. This is just MS marketing hype. –  harrymc Mar 3 '11 at 16:33
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Different applications need different frameworks and I guess there is no backward compatibility , so you might need them all , though you don't need to download them right away.
When you are install an application that needs a specific version of framework you can download them . (They will mostly be needing 2, 3, or 3.5)

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-1 If you have .NET 4 you can run any app built with .NET 1.1+ –  Aaron McIver Mar 3 '11 at 15:19
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@Aaron not in all cases –  Shakehar Mar 3 '11 at 15:27
    
@Aaron Shark is correct. –  Camilo Martin Feb 2 '12 at 22:25
    
@CamiloMartin The FW's as consumed by the consumer are backwards compatible, MS states this themselves. This isn't some pie in the sky dream I am making up. –  Aaron McIver Feb 2 '12 at 23:03
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Not true about Net4 being all you need. I removed all versions and then installed ONLY v4. The first app I tried to run (Powermate) said it could not find the .NET Framework required. So I then installed Net v2 SP2 and the SP2 update and the App ran just fine.

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Right Ken, Microsoft isn't very close to .NET. The .NET Framework 4 is backward-compatible with applications that were built with the .NET Framework versions 1.1, 2.0, 3.0, and 3.5. In other words, applications and components built with previous versions of the .NET Framework will work on the .NET Framework 4. That statement is just hearsay. –  Aaron McIver May 18 '12 at 4:06
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If you have .NET 4 installed you can run any .NET application built with any framework from 1.1 on.

The .NET Framework 4 is backward-compatible with applications that were built with the .NET Framework versions 1.1, 2.0, 3.0, and 3.5. In other words, applications and components built with previous versions of the .NET Framework will work on the .NET Framework 4.

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@Shark That's MS covering their hide...the OP should be fine with a .NET 4 install. –  Aaron McIver Mar 3 '11 at 15:27
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I guess you did not read the next paragraph ...However, in practice, this compatibility can be broken by seemingly inconsequential changes in the .NET Framework and changes in programming techniques –  Shakehar Mar 3 '11 at 15:28
    
maybe , don't have a fresh OS install so all frameworks were installed as they came and haven't faced any issues hence –  Shakehar Mar 3 '11 at 15:30
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@Shark It is MS covering their hide. They can't guarantee what a given developer did for performance gain...especially around threading. To cover their hide they have to propagate that information. VS2010 + .NET 4 allows targeting multiple platforms, ie...3.5, 2.0 etc... If I am building an app targeting the .NET 2 platform for whatever reason I am certainly not shipping .NET 2 redistributable...I am shipping .NET 4. –  Aaron McIver Mar 3 '11 at 15:35
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I know this answer is old, but the linked page explicitly states: By default, an application runs on the version of the .NET Framework that it was built for. If that version is not present and the application configuration file does not define supported versions, a .NET Framework initialization error may occur. In this case, the attempt to run the application will fail. –  pepoluan Sep 6 '13 at 12:29
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