Pass model to PartialAsync view (Razor, MVC) - asp.net-mvc

Question

I have AccountController.cs with below action:
[HttpGet]
[AllowAnonymous]
public IActionResult Register()
{
ViewBag.Registration = GetRegistration();
return View();
}
ViewBag.Registration contains 2 elements and it's ok.
Then I got Registration.cshtml view:
#model Registration <!-- this model I'm using for other form -->
#{
Layout = "_Layout";
}
<!-- some code -->
#await Html.PartialAsync("AllRegistered")
and AllRegistered.cshtml where data from ViewBag.Registration should be displayed:
#model IEnumerable<Registration>
<table>
<tr>
<th>#Html.DisplayNameFor(m => m.Email)</th>
<th>#Html.DisplayNameFor(m => m.City)</th>
</tr>
#if (Model != null && Model.Count() != 0)
{
#foreach (Registration registration in Model)
{
<tr>
<th>#Html.DisplayFor(m => registration.Email)</th>
<th>#Html.DisplayFor(m => registration.City)</th>
</tr>
}
}
</table>
But nothing is generated into view, Model I think is empty.

Answer 1

The PartialAsync method contains an overload which includes the model:
Html.PartialAsync(string partialViewName, TModel model)
You should include the IEnumerable<Registration> (the partial view's model) in that helper.
If GetRegistrations() is returning that IEnumerable, you would define the partial view like this:
#await Html.PartialAsync("AllRegistered", (List<Registration>)ViewBag.Registration)

Answer 2

While Nathan's answer is perfectly correct, it would be more appropriate for this to be a view component. The fact that you want to display all registrations is a view detail that has nothing to do with the purpose of this action. As such, having the action be responsible for retrieving data requires it to have knowledge it doesn't need and shouldn't have.
Instead, add a class like:
public class AllRegistrationsViewComponent : ViewComponent
{
private readonly RegistrationsService _service;
public AllRegistrationsViewComponent(RegistrationService service)
{
_service = service;
}
public async Task<IViewComponentResult> InvokeAsync()
{
// logic behind `GetRegistrations()` here
return View(registrations);
}
}
The reference here to RegistrationsService is just whatever means you're using to retrieve your registrations, to show how to inject that into the component. This might be your context or something else entirely.
Then, create the view Views/Components/AllRegistrations/Default.cshtml with:
#model IEnumerable<Registration>
<table>
<tr>
<th>#Html.DisplayNameFor(m => m.Email)</th>
<th>#Html.DisplayNameFor(m => m.City)</th>
</tr>
#if (Model != null && Model.Count() != 0)
{
#foreach (Registration registration in Model)
{
<tr>
<th>#Html.DisplayFor(m => registration.Email)</th>
<th>#Html.DisplayFor(m => registration.City)</th>
</tr>
}
}
</table>
The AllRegistrations part of the path is based on the name of the view component, without the ViewComponent part, so if you name it differently, adjust here as well.
Finally, in your view:
#await Component.InvokeAsync("AllRegistrations")
Then, your action can just focus on its actual purpose:
[HttpGet]
[AllowAnonymous]
public IActionResult Register()
{
return View();
}