This site is within Microsoft's docs area and gives a good intro into C#, then you can go as far as you like using the menu "tree" down the left or links in the document.
Some people might find this site useful.
https://docs.microsoft.com/en-gb/dotnet/articles/csharp/
Some people might find this site useful.
https://docs.microsoft.com/en-gb/dotnet/articles/csharp/
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