If .NET 3.5 SP1 is missing, can I install 4 directly?

Question

当我在缺少它的系统上需要.NET 3.5 SP1的功能时，安装.NET 4是否安全，或者我是否还需要安装.NET 3.5 SP1？

Answer 1

.NET 4.0 have no relations to .NET 3.5 (.NET 2.0 runtime). It has its own runtime, .NET 4.0 completely separate from .NET 3.5 and lower .NET versions.

So you may install .NET 4.0 without care that you have missing .NET 3.5 SP1. But keep in mind that some applications may require .NET 3.5 SP1. Anyway there is shouldn't be any problems to install .NET 3.5 SP1 later.

Answer 2

short response: yes, it's compatible

long response: if you plan to install it on a customer computer, ensure it's policy does allow this version (big company sometimes need to approve each version of an application before installing it).

[edit] it's compatible but require a tigh modification in the config file http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2009/08/03/installing-net-framework-v4-0-and-running-net-2-0-3-0-3-5-3-5sp1-applications.aspx

Answer 3

If your application targets the .NET 2.0 runtime (used by .NET 2.0, 3.0 and 3.5) and uses functionality from SP 1 of .NET 3.5, you need to install the service pack.

Because .NET 4.0 runs on a different runtime, you can install it without issue side by side.

If your application will be running on the .NET 4.0 runtime, you do not need to install the service pack.