how to get current user in asp.net core code example

Example 1: how get the user show mvc controller core 3.1

string userName = _httpContextAccessor.HttpContext.User.Identity.Name;

Example 2: dotnet core 3.1 get the user that just logged in

private Task<ApplicationUser> GetCurrentUserAsync() => _userManager.GetUserAsync(HttpContext.User);

Example 3: how get the user show mvc controller core 3.1

private readonly IHttpContextAccessor _httpContextAccessor;
//constructor then
_httpContextAccessor = httpContextAccessor;