This is where the file comes to the rescue.
You can also try launching an old application that required .NET 3.5 (like SQL Server 2014 Management Studio or an older game) – it should run without the previous pop-up error. Even with the correct CAB file, you may encounter issues. Here are the most frequent problems and solutions. Error 1: “DISM failed. Error: 0x800f081f – The source files could not be found.” Cause: Windows cannot locate or verify the CAB file signature. Download Microsoft-windows-netfx3-ondemand-package.cab
reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5" /v Install If the output shows 0x1 , installation succeeded. This is where the file comes to the rescue