Question

我遇到了显示为标题的错误。我已经尝试搜索解决方案，但是我得到的只是关于使用ps.setNull(1,Types.NULL);代码块的解决方案。

我一直在使用我制作的课程文档来指导我完成该项目，但是这次我遇到了错误，对于哪一部分出错以及如何检查错误的部分我一无所知。

我用try catch注释对它进行了注释，这意味着我不知道错误发生在哪里或类似的地方。

感谢您阅读我的问题。

这是我的PetRescued模型

// strange

这是我的PetRescued控制器

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; }

}

这是我的PetRescued ViewModel

 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");
}

这是我的PetRescued表格

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

    public PetRescued PetRescueds { get; set; }


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

Answer 1

让我们尝试解决此问题。

首先，让我们更改控制器，使其能够处理由模型绑定程序返回的错误。

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

    var viewModel = new PetRescuedViewModel
    {
        PetSpecies = petspecies
    };

    return View("PetRescued", viewModel);
}

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

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

    viewModel.PetSpecies = _context.PetSpecieses.ToList();  // populate the list again as the contents are lost when the form is submitted.

    return View("PetRescued", viewModel); // validation errors found, so redisplay the same view
}

然后，更改视图以显示错误。我们基本上正在按照this的答案进行建议。

@using (Html.BeginForm("Save", "PetRescued"))
{
    // Displays a summary of all the errors.
    @Html.ValidationSummary() 

    <div class="form-group">
        @Html.LabelFor(m => m.PetRescueds.PetName)
        @Html.TextBoxFor(m => m.PetRescueds.PetName, new { @class = "form-control" })
        // Or you can add this to each property            
        @Html.ValidationMessageFor(m => m.PetRescueds.PetName) 
    </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>
}

以上更改至少会为您提供哪些属性存在问题。

下一步将是解决实际问题。如果您执行上述操作后仍无法解决，请让我知道它是哪个属性，然后看一看。

我猜是public byte PetSpeciesId { get; set; }，但让我们看看。

希望这会有所帮助。

Answer 2

查看您的模型定义

// This means this value is required 
// and should not be greater than 255 characters 
[Required]
[StringLength(255)]
public string PetName { get; set; }

// This means this value is required 
// and should not be greater than 6 characters 
[Required]
[StringLength(6)]
public string PetGender { get; set; }

因此，您没有从客户端应用程序发送值，或者该值大于您指定的限制。将操作方法更改为此，以在后端验证您的模型（永远不要信任客户端输入）

[HttpPost]
public ActionResult Save(PetRescued petRescued)
{
    if (ModelState.IsValid) // Check for errors
    {
        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");
    }
    else
        return View(petRescued); // Return the same view with the original data
                                 // or with the correct model of your view, at least
}

更新

更正您的视图模型以反映正确的数据。这意味着，请确保您将正确的模型发送到后端。 ASP.Net MVC具有称为模型绑定的东西，该机制用于将从客户端接收的数据转换为C＃模型。默认情况下，它通过检测从客户端传递的值的名称并找到具有模型属性的精确映射来工作。这意味着您认为您是在声明这一点

    @Html.TextBoxFor(m => m.PetRescueds.PetName, new { @class = "form-control" })

因此，如果检查浏览器发送的数据，您将看到表单数据包含类似

的内容。

PetRescueds.PetAge: whatever_the_client_typed

不会将映射到您的模型，因为您的模型没有名为PetRescueds的属性，而该属性具有名为PetName的子属性，因此您的动作模型直接是PetRescued模型。因此，可以通过直接指定名称attr来更改视图

    @Html.TextBox("PetName", Model.PetRescueds.PetName, new { @class = "form-control" })

或更改您的操作模型以反映您的视图模型定义。无论哪种方式，您的视图模型都应该通过您的操作和视图保持一致。否则，尽管正确地在视图上填充了空值，或者无论在控制器动作上实际创建了什么，您都将最终在操作模型中接收到空值。

因此，基本上，检查模型定义。确保使用正确的模型定义显示在视图中。确保正确定义了有关您期望在后端控制器中收到的内容的视图。

然后，更改视图以包括从服务器检索到的验证错误

@using (Html.BeginForm("Save", "PetRescued"))
{
<!-- This will show your errors-->
@Html.ValidationSummary()
<div class="form-group">
    @Html.LabelFor(m => m.PetRescueds.PetName)
    <!-- Or you can show errors for each model property -->
    <!-- like this -->
    @Html.ValidationMessageFor(m => m.PetRescueds.PetName);
    @Html.TextBox("PetName", Model.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>
}

您可以在Microsofts's

上了解有关数据验证的更多信息。

Answer 3

您应该使用try和catch方法来查看哪些字段会导致“ EntityValidationErrors ”：

ActionResult保存=>

    try
    {
        _context.SaveChanges();;
    }
    catch (DbEntityValidationException ex)
    {
        var sb = new StringBuilder();

        foreach (var failure in ex.EntityValidationErrors)
        {
            sb.AppendFormat("{0} failed validation\n", failure.Entry.Entity.GetType());
            foreach (var error in failure.ValidationErrors)
            {
                sb.AppendFormat("- {0} : {1}", error.PropertyName, error.ErrorMessage);
                sb.AppendLine();
            }
        }

        throw new DbEntityValidationException(
            "Entity Validation Failed - errors follow:\n" +
            sb.ToString(), ex
            );
    }

然后您将知道哪些记录会产生异常。

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

3 个答案:

更新