Resolving Error Code 0x800f0831: Installing .NET Framework 3.5 on Windows Server 2019

To address the error code 0x800f0831 while installing .NET Framework 3.5 on Windows Server 2019, follow these troubleshooting steps:

1. Verify Installation Status: Navigate to the Control Panel, then to Programs and Features, and check if Microsoft .NET Framework 3.5 is already installed. If present, no further installation is necessary.
2. Utilise DISM Command: Launch Command Prompt as administrator and execute: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\sources\sxs. Adjust 'D:' to match your Windows Server installation media drive letter. This command installs .NET Framework 3.5 directly from your media.
3. Run Windows Update Troubleshooter: Access the Settings app, navigate to Update & Security > Troubleshoot > Windows Update. Utilise the troubleshooter to resolve any update-related issues that might be affecting the installation.
4. Install Latest Windows Updates: Go to Settings > Update & Security, and select 'Check for updates'. Installing the latest updates can sometimes resolve underlying system issues affecting .NET Framework 3.5 installation.
5. Deploy .NET Framework Repair Tool: Download and run Microsoft's .NET Framework Repair Tool. This utility can help fix common problems with .NET Framework setups and installations.