ASP .NET Core 在部分视图中卡住加载视图组件

Question

I'm working on an ASP .NET Core application, and I'm trying to load a view component inside of _LoginPartial. _LoginPartial was created automatically when I created the new project, and my view component is called UserNameViewComponent. The view component should get the logged-in person's username and display it at the top of the screen.

Whenever I log in, the page application gets stuck on the login screen until I stop it. I added a breakpoint to the line in _LoginPartial that calls the view component. When the view component is called it gets my username successfully, but then when it goes back to _LoginPartial it runs the same line of code again to go back to the view component, and this happens forever.

Block of code in _LoginPartial where view component is called:

 @if (SignInManager.IsSignedIn(User))
{
<li class="nav-item">
    <a class="nav-link text-light" asp-area="Identity" asp-page="/Account/Manage/Index" title="Manage">@await Component.InvokeAsync("UserName")</a>
</li>
    <li class="nav-item">
        <form class="form-inline" asp-area="Identity" asp-page="/Account/Logout" asp-route-returnUrl="@Url.Action("Index", "Home", new { area = "" })">
            <button type="submit" class="nav-link btn btn-link text-light">Logout</button>
        </form>
    </li>
}

UserNameViewComponent:

namespace Tangy.ViewComponents
{
public class UserNameViewComponent : ViewComponent
{
    private readonly ApplicationDbContext _db;
    public UserNameViewComponent(ApplicationDbContext db)
    {
        _db = db;
    }

    public async Task<IViewComponentResult> InvokeAsync()
    {
        var claimsIdentity = (ClaimsIdentity)this.User.Identity;
        var claim = claimsIdentity.FindFirst(ClaimTypes.NameIdentifier);

        var userFromDb = await _db.Users.Where(u => u.Id == claim.Value).FirstOrDefaultAsync();

        return View(userFromDb);
    }

}

Default.cshtml:

@model Tangy.Models.ApplicationUser
@{
    ViewData["Title"] = "Default";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

Hi @Model.FirstName @Model.LastName <i class="far fa-user"></i>

Does anyone know what I'm doing wrong here?

Answer 1

It looks like the issue is that _LoginPartial is contained in _Layout and rendering your View Component which then references _Layout . This will create a circular reference and the code for your view component (and the code for _Layout ) will be called over and over.

_Layout -> _LoginPartial -> Default.cshtml (from view component) -> _Layout -> _LoginPartial -> Default.cshtml (from view component ) on and on and on.....

setting the Layout to null in the ViewComponent's view should solve your issue.

@{
    ViewData["Title"] = "Default";
    Layout = null;
}