Which version of the .NET Framework is IIS using for my AppPool?

Question

.Net Framework 4.5 was installed on my machine and on the IIS Application Pool, I set the .NET CLR version to 4.0.

My question is when running .NET code in this IIS site, which framework version is it using: 4.0 or 4.5 ?

Please see below screen shots.

Answer 1

The AppPool's .NET CLR Version is different from the .NET Framework Version.

The .NET CLR Version 4.0 is the CLR base for the following .NET Framework Versions:

• 4
• 4.5 (including 4.5.1 and 4.5.2)
• 4.6 (including 4.6.1 and 4.6.2 Preview)

So having a .NET CLR Version of 4.0 just means you support the above Frameworks, which will run under their deployed framework version.

Source: https://docs.microsoft.com/en-us/dotnet/standard/clr#clr-versions

Update Feb 2020:

Here is a full mapping of CLR to .NET Framework versions, based off this official documentation. https://docs.microsoft.com/en-us/dotnet/framework/migration-guide/versions-and-dependencies#version-information

CLR 1.0

.NET Framework 1.0

---

CLR 1.1

.NET Framework 1.1

---

CLR 2.0

.NET Framework 2.0

.NET Framework 3.0

.NET Framework 3.5

---

CLR 4

.NET Framework 4

.NET Framework 4.5

.NET Framework 4.5.1

.NET Framework 4.5.2

.NET Framework 4.6

.NET Framework 4.6.1

.NET Framework 4.6.2

.NET Framework 4.7

.NET Framework 4.7.1

.NET Framework 4.7.2

.NET Framework 4.8