Installing .NET Framework 3.5 on Windows Server 2012 R2 Installing .NET Framework 3.5 on Windows Server 2012 R2 is a common requirement for running legacy applications, but it often encounters errors like 0x800F0906 or 0x800F081F because the necessary source files are not included in the default installation image to save space.
Mount the ISO:
File Integrity: If downloading the CAB file individually rather than using an ISO, verify the file hash to ensure it hasn't been tampered with. Installing
Open PowerShell as Administrator or Command Prompt as Administrator. Installing
Processing 1 of 1 - Adding package Microsoft-Windows-NetFx3-OnDemand-Package~31bf3856ad364e35~amd64~~6.3.9600.16384 [==========================100.0%==========================] The operation completed successfully. Installing