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@mshobohm commented on Thu Nov 14 2019
With dotnet --list-sdks I get some old SDKs that I do not get displayed in the "Windows Add / Remove Programs dialog box". Consequently, they can probably only be deleted by deleting in the Explorer, I hope that is residue-free. The site could write something about this topic.
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@srvbpigh commented on Fri Nov 15 2019
Hello, @mshobohm
Thank you for your feedback.
We are actively reviewing your comments and will get back to you soon.
Kind regards,
Microsoft DOCS International Team
The preceding is correct. Additionally, for the preview SDK versions it lists that VS installed, you get the following message

cc @livarcocc and @johnbeisner
try reinstall the old version and then uninstall again.
Meanwhile I did a cure by renaming the c:\Program files\dotnet folder (3,7 GB) and installing only the latest SDK. My computer didnt explode, so I think these "irregular SDK versions" can safely be deleted in the explorer. Perhaps one time we could have "dotnet --install-sdk" and "dotnet --remove-sdk" harmonizing the download/installation/update on all operating systems, also for the runtime.
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Meanwhile I did a cure by renaming the c:\Program files\dotnet folder (3,7 GB) and installing only the latest SDK. My computer didnt explode, so I think these "irregular SDK versions" can safely be deleted in the explorer. Perhaps one time we could have "dotnet --install-sdk" and "dotnet --remove-sdk" harmonizing the download/installation/update on all operating systems, also for the runtime.