private async Task <ClaimsIdentity> AuthenticateAsync <TUser>(UserManager <TUser> _userManager, SignInManager <TUser> _signinManager, string username) where TUser : class
{
var user = await _userManager.FindByNameAsync(username);
if (user == null)
{
return(null);
}
return(await _signinManager.AuthenticateAsync(user));
}