https://www.microsoft.com/en-us/download/details.aspx?id=42637
(Note: Microsoft may redirect to a newer page, but the GUID 42637 is permanent for .NET 4.5.1 and 4.5.2. For pure .NET 4.5, see the historical note below.)
If you are managing a build server (Azure DevOps Agent, GitHub Actions runner, Jenkins):
Cause: You already have a newer version (e.g., 4.7 or 4.8). The Developer Pack will refuse to install because the runtime is superseded. Fix: You don’t need the full Developer Pack. Instead, install the .NET Framework 4.5 Targeting Pack from the Visual Studio Installer (Individual Components → SDKs, libraries, and frameworks → “.NET Framework 4.5 targeting pack”).
Microsoft officially hosts the Developer Pack on their servers. You can grab it directly below: net framework 45 developer pack link
Download .NET Framework 4.5 Developer Pack (Web Installer)
(Note: This is usually a small web installer that will download the necessary components during setup. If you need the offline installer for a machine without internet access, look for the specific "Offline Installer" link on that same Microsoft page, though the Developer Pack is typically web-based.)
You might think, “I have .NET 4.8 installed. Isn’t that backward-compatible?” https://www
Yes and no. The .NET Framework 4.x series is in-place updated. Installing .NET 4.8 replaces the 4.5 runtime on your machine. However, the reference assemblies for .NET 4.5 are not automatically retained. If you open a project that specifically targets .NET 4.5 (common in CI/CD pipelines or legacy maintenance), Visual Studio will look for the exact 4.5 reference assemblies. If it finds only 4.8 assemblies, it may crash or fail to load IntelliSense.
Thus, the Developer Pack is essential for:
Open regedit and navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319\SKUs\.NETFramework,Version=v4.5
If that key exists (on 64-bit Windows), the targeting pack is registered.
Ensure all instances of Visual Studio, Blend, or MSBuild processes are closed. Otherwise, file locks may cause the installation to fail or require a reboot.
Note: If you are setting up a modern development environment, Microsoft recommends installing the .NET Framework 4.8 Developer Pack, as it is the last major version of .NET Framework and includes support for all previous versions (including 4.5) via multi-targeting. (Note: Microsoft may redirect to a newer page,