Mailbag: Should I re-install the versions of the .NET Framework in a specific order?

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Question:

I used the instructions and the cleanup tool in this blog post to remove all versions of the .NET Framework from my computer, and now I want to re-install them.  Do I need to re-install them in any specific order?

Answer:

In general, the versions of the .NET Framework allow you to install in any order you choose.  However, I recommend installing in reverse order from newest to oldest, like this:

  1. .NET Framework 4
  2. .NET Framework 3.5 SP1 (this will install the .NET Framework 2.0 SP2 and 3.0 SP2 behind the scenes so you do not have to install them separately)
  3. .NET Framework 1.1 (if you have any programs installed that need it, this blog post can help you decide whether or not you need it)

Most programs do not specifically require the .NET Framework 1.0 so I didn't list it above.  If you do need the .NET Framework 1.0, you will have to install it before installing the .NET Framework 4 because .NET Framework 4 setup blocks future installation attempts for the .NET Framework 1.0.  If you need the .NET Framework 1.0, I recommend installing in this order:

  1. .NET Framework 3.5 SP1 (this will install the .NET Framework 2.0 SP2 and 3.0 SP2 behind the scenes so you do not have to install them separately)
  2. .NET Framework 1.1 (if you have any programs installed that need it, this blog post can help you decide whether or not you need it)
  3. .NET Framework 1.0 (if you have any programs installed that need it, this blog post can help you decide whether or not you need it)
  4. .NET Framework 4

Even though it is a little counter-intuitive, there are a couple of reasons that I recommend installing in reverse order:

  • To help avoid some possible setup bugs in older versions of the .NET Framework – there are a couple of setup bugs (like this and this) in older versions of the .NET Framework that are fixed in service packs and later versions.  Installing a later version of the .NET Framework first will update some files that are shared by all versions of the .NET Framework, and that will allow you to avoid these bugs when installing older versions of the .NET Framework.
  • To minimize the number of separate downloads and installs – if you install the .NET Framework 3.5 SP1 first, it will automatically install the .NET Framework 2.0 SP2 and 3.0 SP2 for you, so you don’t need to install them separately.  Also, if you install older versions of the .NET Framework 2.0 and 3.0 before installing the .NET Framework 3.5 SP1, the 3.5 SP1 installer will automatically uninstall them as a part of its install process.  That means you will just end up wasting time if you install the .NET Framework 2.0 and 3.0 before installing the .NET Framework 3.5 SP1.

<update date="1/31/2011"> Added a separate set of installation instructions for cases where the .NET Framework 1.0 is required because .NET Framework 4 setup prevents the .NET Framework 1.0 from being installed after it. </update>