How to install .NET 4 Framework in Windows 10
How can I install the .NET 4.0 Framework in Windows 10? .NET 4.6 is already installed but I want to have .NET 4 Framework (without modifying the registry).
Turning on and off Windows features in control panel does not have any effect.
Answer
From the download page for the "Microsoft .NET Framework 4.6" (emphasis mine):
The Microsoft .NET Framework 4.6 is a highly compatible, in-place update to the Microsoft .NET Framework 4, Microsoft .NET Framework 4.5, Microsoft .NET Framework 4.5.1 and Microsoft .NET Framework 4.5.2.
On other words, having .NET 4.6 installed (it's part of Windows 10 so you need not manually install it) means you have .NET 4.0, 4.5, 4.5.1, 4.5.2 and 4.6 installed and can run code targeting any of those framework versions without making any modifications to your Windows installation.
You cannot install .NET 4.0 when you have a later version installed as each version is an in-place update to the last.
If, however, your problem is with opening a project which targets .NET 4.0.1, 4.0.2, or 4.0.3 in Visual Studio on Windows 10, you may need to download one of the targeting packs:
- Multi-Targeting Pack for .NET 4.0.1
- Multi-Targeting Pack for .NET 4.0.2
- Multi-Targeting Pack for .NET 4.0.3
as I'm not sure they are installed.