HyperCube/Areas/Identity/Pages/Shared/_LoginPartial.cshtml

@using Microsoft.AspNetCore.Identity
@inject SignInManager<IdentityUser> SignInManager
@inject UserManager<IdentityUser> UserManager
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

<ul class="navbar-nav">
@if (SignInManager.IsSignedIn(User))
{
    <li class="nav-item">
        <a  class="nav-link text-dark" asp-area="Identity" asp-page="/Account/Manage/Index" title="Manage">@User.Identity.Name</a>
    </li>
    <li class="nav-item">
        <form class="form-inline" asp-area="Identity" asp-page="/Account/Logout" asp-route-returnUrl="/" method="post">
            <button  type="submit" class="nav-link btn btn-link text-dark">Выход</button>
        </form>
    </li>
}
else
{
    <li class="nav-item">
        <a class="nav-link text-dark" asp-area="Identity" asp-page="/Account/Register">Регистрация</a>
    </li>
    <li class="nav-item">
        <a class="nav-link text-dark" asp-area="Identity" asp-page="/Account/Login">Вход</a>
    </li>
}
</ul>