选择列表未从ViewModel ASP.NET填充

Question

The select list in one of my views is not populating from the View Model and I can't figure it out. The other parts of the view model behave as expected. The view is a partial view, if that matters.

Here is the code for the view:

 @model Workout_Tracker.ViewModels.AddExerciseViewModel
        <form >
           <div class="individualContainer">
                <label asp-for="ExerciseTypeID"></label>
                <select asp-for="ExerciseTypeID" asp-items="Model.ExercisesTypes">
                </select>
                <label asp-for="Reps"></label>
                <input type="number" asp-for="Reps" />
               </div>
            </form>

Here is the View Model:

public class AddExerciseViewModel
{
    [Display(Name ="Weight")]
    [Required(ErrorMessage="You must enter a weight.")]
    public int Weight { get; set; }

    public int Reps { get; set; }

    //this sets will be used to create the sets in the Exercise_Sets table
    public int Sets { get; set; }

    public int WorkoutID { get; set; }

    public int ExerciseTypeID { get; set; }

    public List<SelectListItem> ExercisesTypes { get; set; }

    public AddExerciseViewModel(IEnumerable<ExerciseType> exercises) {

        ExercisesTypes = new List<SelectListItem>();
        foreach (ExerciseType ex in exercises)
        {
            ExercisesTypes.Add(new SelectListItem
            {
                Value = ex.ID.ToString(),
                Text = ex.Name                  
            });
        }
    }

    public AddExerciseViewModel() {

    }
}

Here is the controller:

  public IActionResult WorkoutSelector() {
        IList<ExerciseType> exerciseTypes = context.ExerciseTypes.ToList();

        AddExerciseViewModel addExerciseViewModel1 = new AddExerciseViewModel(exerciseTypes);

        return PartialView("_WorkoutSelector", addExerciseViewModel1);
    }

Here is the ExerciseType class:

 public class ExerciseType
{
    public int ID { get; set; }

    public string Name { get; set; }

}

Answer 1

I don't normally create ActionResult methods in my controllers for the purpose of rendering partials, so I can't directly speak to extenuating circumstances surrounding your MVC pipeline.

Given a traditional ASP.NET MVC project, however, I tend to render my partials not by invoking actions, but as includes within my views using ViewBag as a reliable alternative for supplementing additional data to any view/partial in context as necessary.

~/Views/Workout/Welcome.cshtml

<div>
  <h2>Workout</h2>
  <p>Select your workout below:</p>

  @Html.Partial("~/Views/Shared/_WorkoutSelector.cshtml", ViewBag.MyExerciseViewModel);
</div>

Then in your controller, just load whatever is you needed in your main action and get rid of the partial action:

public class WorkoutController : Controller {
  ...

  public ActionResult Welcome() {
    ViewBag.MyExerciseViewModel = new AddExerciseViewModel(context.ExerciseTypes.ToList());

    return View();
  }
}

By the way, are you disposing that DbContext properly? :)