if you may get an error message as per image on the right by trying to install DotNet (.Net) on windows 10 and you are using a WSUS server, this error may occur of the .net installer is not approved in WSUS.

Follow below steps:

1) As a temporary workaround, change the registry key “UseWUServer” to 0 located at HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU

2) restart the windows update service

3) start powershell as administrator

4) type in the powershell       Dism /online /enable-feature /featurename:NetFX3 /All /Source:R:\sources\sxs