Net Framework 45 Developer Pack Link -

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.

4.5 is reaching end-of-support on many modern Windows versions; consider upgrading to 4.6.2 or 4.8 if your project allows. net framework 45 developer pack link

Unlike a standard runtime installer, the Developer Pack (also known as a Targeting Pack ) contains: Ensure all instances of Visual Studio, Blend, or

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. Unlike a standard runtime installer, the Developer Pack

(If you want, I can provide a concise download link and exact Visual Studio installer steps.)