# NET Framework 3.5 Question

**URL:** <https://boards.straightdope.com/t/net-framework-3-5-question/483387>\
**Category:** Factual Questions\
**Created:** [January 28, 2009, 3:28pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387 "2009-01-28T15:28:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\
**Post date:** [January 28, 2009, 3:28pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387/1 "2009-01-28T15:28:19Z")

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Just got notified that NET Framework 3.5 is ready, and downloaded it.

The question that I have is that versions 1.1, 2.0 and 3.0 are still on the computer. Is it advisable to uninstall those earlier versions, as 3.5 is supposed to include them all? Or just leave well enough alone?

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**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\
**Post date:** [January 28, 2009, 3:46pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387/2 "2009-01-28T15:46:47Z")

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Chances are as an end user you won’t ever need any of the frameworks, unless you download an app that needs them. I’m not sure how popular desktop apps are that use the frameworks.

As far as I know, 3.5 is backwards compatible back to 2.0. 1.1 is sort of its own (messy) thing.

You can safely remove the others, and if you come across an app that needs them you can always get them again.

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**Author:** ![dmatsch](https://avatars.discourse-cdn.com/v4/letter/d/3be4f8/32.png) [@dmatsch](https://boards.straightdope.com/u/dmatsch)\
**Post date:** [January 28, 2009, 4:35pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387/3 "2009-01-28T16:35:11Z")

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I’m a C# developer and according to M$ they should all be backwards compatible.

Just do what my company does. Make changes and see what breaks.

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**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\
**Post date:** [January 28, 2009, 6:17pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387/4 "2009-01-28T18:17:11Z")

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> [@dmatsch](#):
>
> I’m a C# developer and according to M$ they should all be backwards compatible.
> 
> Just do what my company does. Make changes and see what breaks.

Thanks guys, I’ll give it a try, but create a restore point first.

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**Author:** ![LilShieste](https://avatars.discourse-cdn.com/v4/letter/l/9f8e36/32.png) [@LilShieste](https://boards.straightdope.com/u/LilShieste)\
**Post date:** [January 28, 2009, 9:55pm UTC](https://boards.straightdope.com/t/net-framework-3-5-question/483387/5 "2009-01-28T21:55:03Z")

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Here’s a rundown of how the versions relate to one another:

[ul]  
[li] Version 2.0 functionally **replaces** version 1.1[/li][li] Version 3.0 **builds on top** of version 2.0[/li][li] Version 3.5 **builds on top** of version 3.0[/li][/ul]  
So, technically, you can’t have version 3.0/3.5 without having version 2.0 installed. The reason version 1.1 was left in place (i.e., not replaced by 2.0 upon installation) is for backwards-compatibility purposes.

[Here’s an MSDN page with some additional information.](http://msdn.microsoft.com/en-us/netframework/aa663314.aspx)