.NET Framework is a piece of software, developed by Microsoft, that provides a number of basic functions to the Windows platform.
Any application developed in “.NET” has the benefit of a range of different updates, features, and libraries that are not available without the package.
The tradeoff is that for applications to work on your system, you need to have .NET installed and running. This error tends to show up when you try to install version 3.5.
The solution, according to Microsoft, is to perform a core update of the Windows operating system from an ISO file. This is not a major issue, but there are a number of other steps you can take as well.
Cause
The error is usually displayed with the following message:
Error: 0x800f0906
The source files could not be downloaded.
0x800F0906 – CBS_E_DOWNLOAD_FAILURE
Error code: 0x800F0906
The cause of the problem is that the “Windows Image” is corrupted.
This means that certain files, settings, and options within the Windows operating system will not work properly, causing the error to appear.
The fix is a combination of updating Windows and making sure there aren’t any core bugs with your setup, etc.
Solution
1.CFS/DYSMO
The “SFC” (System File Checker) + “DISM” (Deployment Image Servicing and Management) applications are standard elements of the Windows ecosystem.
While they are very effective, unfortunately they are not that good at fixing the 0x800f0906 error.
However, they are the least intrusive way to work towards a solution and therefore should be tried at least before doing more heavy lifting.
- Press “Windows” + “S” keys on the keyboard
- This will open the “search” box, in which you need to type “CMD”
- From the list that appears, right-click “Command Prompt” with your mouse and choose “Run as administrator”
When it loads, type the following:
- “SFC /scan now”
- This will run for some time, after which it will show progress “results” (should be ok)
- Once complete, type “DISM /Online /Cleanup-Image /RestoreHealth”
- This will perform another scan – let it run and then at the end it should show you the results.
- Restart your PC
The purpose of this is to clean up any of the “system” files that may be present on your system.
Windows has a large number of “system files” that are necessary for it to function at its best. Both SFC + DISM can fix most of these problems, but not all.
It is very likely that the error 0x800f0906 will not be resolved with this step alone.
2.Internet connectivity
The next step is to check internet connectivity.
This may sound trivial, but it often happens that a lot of systems will have specific problems with the way their internet is connected.
If you want to make sure your computer can download the appropriate files/updates, you need to make sure your internet is fully working:
- Load your preferred web browser
- Try connecting to the “Windows Update” website
If the connection works in a browser, you’ll need to try it from CMD:
- Press “Windows” + “S” keys on your keyboard
- In the “search” box that appears, type “CMD”
- Right click on the listings and select “Run as administrator”
- Type: “ping update.microsoft.com” (no spaces)
- If the ping is successful, you should be fine
3. Group Policy Settings
If the above doesn’t work, you’ll need to make sure your user account has the correct permissions to download various updates (such as .NET).
- Press “Windows” + “S” keys on your keyboard
- In the “Search” box, type “Group Policy” and click the “Edit Group Policy” list that appears
In the applet that loads, do the following:
- Select “Computer Settings” on the left sidebar
- Select “Administrative Templates” + “Systems”
- In the list that appears, select “Specify settings for installation and repair of optional components”
- Select “Enabled” in the settings menu on the left
- Click OK”
- Try to install .NET again
If this does not work, it is likely that the “source” of the installation is corrupted or damaged. To fix this, we can use the Windows installation media.
4. Windows installation media
Lastly, you want to try using the Windows installation media to create a set of new files that any .NET installation can use.
This is a common practice, and can be done by following the steps below:
- Search for “Windows Media Creation Tool”
- Click on the first Microsoft site that appears
- Click the “Download Tool Now” button
- Save the file to your hard drive and upload it
- Select “Create ISO”
- Follow the steps to create an ISO (which you then need to double-click to “mount”)
Once the ISO is mounted, you will be able to reference your files as needed.
To do this effectively, you’ll be able to use the third step, except this time you’ll be able to manage the “source” to include any installation files your system might need.
You can do this using the following:
- Follow the steps in “Group Policy Settings” in step 3
- Before clicking “OK”, enter “[[ISO drive path]]/sources/sxs” in the “Alternate Source File Path” box
- Run “gpupdate /force”
- Add the .NET function
- Restart your PC
If the above doesn’t work, it suggests you have a deeper problem within Windows.
To resolve this, you’ll need to talk to someone with direct access to your system or people who can categorize the error for you. Obviously, an article from the Internet can’t do that.