Change source control plug-in in Visual Studio

What actually helped me, I could not find in my Asp.net core solution folder any svn file or .git, but it was in C:\Users\NAME, deleted there .git file, it was HIDDEN. Then in vs automatically source control changed from git to TFVS. however it somehow created in my solution folder git files, deleted once more and it started to work fine.

Suggestion: Don't bother with switching. Remove it from source control (SVN) and check it in anew (git). Or, if removing it by Visual Studio tools doesn't work, here's how you do it manually:

1. Close Visual Studio;
2. Delete the .svn folder
3. Open the .SLN file in notepad, find the lines which specify the SCC provider, and delete them.
4. Open the solution in Visual Studio again - it should not be under source control anymore and you should be able to check it in git.

Edit: Manually removing this from the .sln file did the trick:

GlobalSection(SubversionScc) = preSolution
    Svn-Managed = True
    Manager = AnkhSVN - Subversion Support for Visual Studio
EndGlobalSection

The easier way to do it is a two steps process which can be done withput leaving Visual Studio:

1. Open the menu option File > Source Control > Change Source Control. In the dialog use the Disconnect button.

2. As described in the question itself, open the menu Tools > Options, and change the Source Control to git. This time it will change it without complaining at all.