.NET Framework 3.5 was released in 2007 alongside Windows Vista. Many business applications, games, and specialized tools were built specifically on this version. Even though Windows 10 and 11 ship with .NET Framework 4.8 (or newer), Microsoft does include version 3.5 by default due to security and image size considerations.
If your environment favors PowerShell scripts, you can use the Add-WindowsCapability or Add-WindowsFeature equivalents.
Run the following command, adjusting the path to your file:
Offline installations can sometimes fail due to syntax mistakes or underlying OS configurations. Here are the most common error codes and how to fix them: Error Code Source files could not be downloaded or found.
After restarting, you can verify that .NET Framework 3.5 is successfully installed.
Once you have safely located or positioned the .cab file, choose one of the following terminal methods to deploy it. Method 1: Deployment Image Servicing and Management (DISM)
Only if it is sourced from a legitimate Windows ISO file, as described above.
Without this .cab file, Windows will try to download the feature from Windows Update. If your PC is offline, behind a corporate firewall, or if Windows Update is broken, the installation will fail – hence the need for the offline .cab package.
建议您将对应版本的 CAB 文件保存在安全的 U 盘或网络共享中。这不仅能为您的系统运行旧款关键软件提供坚实基础，让您在无网环境下也能游刃有余，还能为同事或客户提供极大的便利。
If you did not rename the file, replace C:\netfx3.cab with the full path to the original CAB file, for example: C:\microsoft-windows-netfx3-ondemand-package~31bf3856ad364e35~amd64~~.cab .
Once the DISM tool reports that the operation completed successfully, restart your computer to finalize the installation.
: Deploy features on machines without an active connection to Windows Update.
