Always use dotnet.microsoft.com to avoid malware.
If you open an older project in Visual Studio and see an error stating "The target framework '.NETFramework,Version=v4.5' was not found," it means you are missing this pack. Without it, you cannot: Compile code targeting .NET 4.5. net framework 45 developer pack link
The Developer Pack (also known as the Targeting Pack) is different from the standard runtime: Always use dotnet
This is the most stable version of the 4.5 branch. You can find it at the Official Microsoft Download Center . Version=v4.5' was not found