estou usando a versao 3.1 do framework e me deparei com o erro do video mesmo fazendo todos os passos do professor:
An unhandled exception occurred while processing the request. InvalidOperationException: The view 'formulario' was not found. The following locations were searched: /Views/Cadastro/formulario.cshtml /Views/Shared/formulario.cshtml /Pages/Shared/formulario.cshtml
pare resolver quando ele abre o arquivo csproj eu precisei apagar toda essa tag:
<ItemGroup>
<Content Remove="Views\Cadastro\Formulario.cshtml" />
</ItemGroup>e depois disso funcionou.