Net Framework 45 Developer Pack Link -

The solution is almost always the same:

If you are a Windows developer working with Visual Studio 2012, 2013, or even older legacy applications in VS 2015/2017, you have likely encountered a frustrating build error: “TargetFrameworkAttribute is missing” or “Reference assemblies for framework .NETFramework,Version=v4.5 were not found.” net framework 45 developer pack link

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. The solution is almost always the same: If