handling form in controller using viewmodel with two parameters - asp.net-mvc

Question

I want to save values from a form to my database. I'm using a viewmodel with an selectlist property and a regular model. The value from the dropdown doesn't get saved. Despite being a trivial and seemingly pretty simple thing, I'm pretty lost.
Below my code:
Model:
public class Movie
{
public int MovieID { get; set; }
public string Name { get; set; }
public int StudioID { get; set; }
public Studio Studio { get; set; }
}
My ViewModel:
public class CreateMoviesViewModel
{
public Movie Movie { get; set; }
public IEnumerable<SelectListItem> StudiosSelectList { get; set; }
}
My Controller:
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create(CreateMoviesViewModel movieViewModel)
{
if (ModelState.IsValid)
{
_context.Add(movieViewModel);
await _context.SaveChangesAsync();
return RedirectToAction(nameof(Index));
}
movieViewModel.StudiosSelectList = new SelectList(_context.Studios.AsNoTracking(), "StudioID", "Name");
return View(movieViewModel);
And finally, my Form:
<form asp-action="Create">
<div asp-validation-summary="ModelOnly" class="text-danger"></div>
<input type="hidden" asp-for="Movie.MovieID" />
<div class="form-group">
<label asp-for="Movie.Name" class="control-label"></label>
<input asp-for="Movie.Name" class="form-control" />
<span asp-validation-for="Movie.Name" class="text-danger"></span>
</div>
<div class="form-group">
<label asp-for="Movie.StudioID" class="control-label"></label>
#Html.DropDownListFor(m => m.StudiosSelectList, Model.StudiosSelectList, "Select one")
</div>
<div class="form-group">
<input type="submit" value="Create" class="btn btn-default" />
</div>
</form>
It is probably something wrong with my dropdown list, or with the logic described in the POST section. Any help is greatly appreciated!

Answer 1

You need to pass the selected dropdown value to your model:
public class CreateMoviesViewModel
{
public int SelectedValueId { get; set; } // <-- not sure what are you selecting, this could be MovieId if you are selecting a movie
public Movie Movie { get; set; }
public IEnumerable<SelectListItem> StudiosSelectList { get; set; }
}
Then you can use:
#Html.DropDownListFor(m => m.SelectedValueId, m.StudiosSelectList)
This way, the selected value Id would be passed to your model.
SelectValueId should be initialized to the default value that you want to display in the Dropdown.