Simply with Winforms :
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How can I create a .Net 5 window without Xaml?
Please, no legacy frameworks like Winforms or WPF. I would use UWP, except it has a couple of significant issues ...
The first two issues make UWP unsuitable for games and particular kinds of application interface design. Even when UWP and .Net 5 are made to be compatible, only one of these deal-breaking issues is going to be resolved.
Simply with Winforms :