问一个或多个实体的验证失败。有关更多详细信息，请参见'EntityValidationErrors‘属性。ASP.NET MVC

EN

public class PetRescued
{
    public int Id { get; set; }

    [Required]
    [StringLength(255)]
    public string PetName { get; set; }

    public int PetAge { get; set; }

    [Required]
    [StringLength(6)]
    public string PetGender { get; set; }

    public short PetWeightInKg { get; set; }

    public DateTime DateWhenRescued { get; set; }

    public PetSpecies PetSpecies { get; set; }

    public byte PetSpeciesId { get; set; }

}

 public ActionResult New() //populate form
    {
        var petspecies = _context.PetSpecieses.ToList();

        var viewModel = new PetRescuedViewModel
        {
            PetSpecies = petspecies
        };

        return View("PetRescued", viewModel);
    }

[HttpPost]
public ActionResult Save(PetRescued petRescued)
{
    if (petRescued.Id == 0)
        _context.PetRescueds.Add(petRescued);
    else
    {
        var petRescuedInDb = _context.PetRescueds.Single(c => c.Id == petRescued.Id);
        petRescuedInDb.PetName = petRescued.PetName;
        petRescuedInDb.PetAge = petRescued.PetAge;
        petRescuedInDb.PetGender = petRescued.PetGender;
        petRescuedInDb.PetWeightInKg = petRescued.PetWeightInKg;
        petRescuedInDb.PetSpeciesId = petRescued.PetSpeciesId; //strange
        petRescuedInDb.DateWhenRescued = petRescued.DateWhenRescued;
     }

    _context.SaveChanges();
    return RedirectToAction("Index", "PetRescued");
}

public class PetRescuedViewModel
{
    public IEnumerable<PetSpecies> PetSpecies { get; set; }

    public PetRescued PetRescueds { get; set; }


    public PetRescuedViewModel()
    {
        PetRescueds = new PetRescued(); 
    }
}

@using (Html.BeginForm("Save", "PetRescued"))
{
<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.PetName)
    @Html.TextBoxFor(m => m.PetRescueds.PetName, new { @class = "form-control" })
</div>

//strange
<div class="form-group">
    @Html.LabelFor(m => m.PetSpecies)
    @Html.DropDownListFor(m => m.PetRescueds.PetSpeciesId, new SelectList(Model.PetSpecies, "Id", "SpeciesName"), "Select A Species", new {@class = "form-control"})    
</div>

<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.PetAge)
    @Html.TextBoxFor(m => m.PetRescueds.PetAge, new { @class = "form-control" })
</div>

<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.PetGender)
    @Html.TextBoxFor(m => m.PetRescueds.PetGender, new { @class = "form-control" })
</div>

<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.PetWeightInKg)
    @Html.TextBoxFor(m => m.PetRescueds.PetWeightInKg, new { @class = "form-control" })
</div>

<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.DateWhenRescued)
    @Html.TextBoxFor(m => m.PetRescueds.DateWhenRescued, "{0:d MMM yyyy}", new { @class = "form-control" }) 
</div>

@Html.HiddenFor(m => m.PetRescueds.Id)
<button type="submit" class="btn btn-primary">Save</button>
}