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If you'd like to dive deeper,5 to newer framework versions (e.g., 4.8 or .NET 6/7/8)
Microsoft still hosts the 4.5.1 Developer Pack on their Download Center:
The Developer Pack is designed to install the targeting tools even if a newer runtime exists. If the installer fails entirely, you may need to use the Visual Studio Installer application to modify your workload and add individual targeting packs under the "Individual Components" tab. Missing Framework Option in Visual Studio microsoft .net framework 4.5 developer pack download
Because official direct standalone installer links for the older 4.5 developer pack have been retired from the main Microsoft download pages, modern developers use NuGet reference assemblies to restore compilation capability.
Microsoft previously signed .NET Framework content with certificates using the SHA1 algorithm. As part of evolving industry standards, these certificates expired. If you'd like to dive deeper,5 to newer
Even with the NuGet method, you may encounter issues:
Up to 4.5 GB of available space depending on your system architecture and current updates. Step-by-Step Download and Installation Guide Step 1: Locating the Official Download Microsoft previously signed
I can provide step-by-step instructions to upgrade your project file to a newer, secure version of .NET. Share public link
The .NET Framework 4.5 is a highly compatible, in-place update to the .NET Framework 4. The "Developer Pack," specifically, is a version of the .NET Framework designed for software developers. It includes the .NET Framework runtime (the redistributable components required to run apps) but also adds the necessary tools, SDKs, and targeting packs. This makes it possible to develop applications that specifically target .NET Framework 4.5 within an Integrated Development Environment (IDE) like Visual Studio, ensuring your code compiles and runs correctly against that version.
Instead of relying on system-wide installations, consider copying reference assemblies directly into your project's source control for consistent builds across different developer machines.
Windows 7 SP1, Windows Server 2008 R2 SP1, Windows Server 2008 SP2, and Windows Vista SP2.
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