小贝子编程

填充视图模型的正确方法



我正在开发一个用于工作的Web应用程序，并且我正在使用标准的CRUD样式交互。但是，有些字段我不希望用户更新，因此我将它们从视图中删除。但是，如果我没有显式设置这些字段，则在数据库中更新模型时会清除这些字段。

我关心为我的视图模型填充字段的正确方法是什么。

我想出的粗略想法是这样的：

我的视图模型：

public class EditSoftwareTrackingViewModel 
{
    public EditSoftwareTrackingViewModel(SoftwareTracking model)
    {
        Id = model.Id;
        SoftwareId = model.SoftwareId;
        ComputerId = model.ComputerId;
        SoftwareActionId = model.SoftwareActionId;
        LastModified = model.LastModified;
        Computer = model.Computer;
        Software = model.Software;
        SoftwareAction = model.SoftwareAction;
    }
    public int Id { get; set; }
    [DisplayName("Software")]
    public int SoftwareId { get; set; }
    [DisplayName("Computer")]
    public int ComputerId { get; set; }
    [DisplayName("Software Action")]
    public int SoftwareActionId { get; set; }
    [DisplayName("Last Modified")]
    public DateTime? LastModified { get; set; }
    public virtual Computer Computer { get; set; }
    public virtual Software Software { get; set; }
    public virtual SoftwareAction SoftwareAction { get; set; }
}

我的主要模型

[Table("asset.SoftwareTracking")]
public partial class SoftwareTracking
{
    public int Id { get; set; }
    [DisplayName("Software")]
    public int SoftwareId { get; set; }
    [DisplayName("Computer")]
    public int ComputerId { get; set; }
    [DisplayName("Date Entered")]
    public DateTime? EnteredDate { get; set; }
    [DisplayName("Software Action")]
    public int SoftwareActionId { get; set; }
    [DisplayName("Last Modified")]
    public DateTime? LastModified { get; set; }
    public virtual Computer Computer { get; set; }
    public virtual Software Software { get; set; }
    public virtual SoftwareAction SoftwareAction { get; set; }
}

我的控制器使用视图模型

    public ActionResult Edit(int? id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        EditSoftwareTrackingViewModel softwaretracking = new EditSoftwareTrackingViewModel(db.SoftwareTrackings.Find(id));
        if (softwaretracking == null)
        {
            return HttpNotFound();
        }
        GeneratePageData(softwaretracking.Software.Id);
        return View(softwaretracking);
    }
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Edit(EditSoftwareTrackingViewModel softwaretracking)
    {
        if (ModelState.IsValid)
        {
            softwaretracking.LastModified = DateTime.Now;
            var softwareTrack = db.SoftwareTrackings.Find(softwaretracking.Id);
            softwareTrack = new SoftwareTracking
            {
                Computer = softwaretracking.Computer,
                ComputerId = softwaretracking.ComputerId,
                LastModified = softwaretracking.LastModified,
                Software = softwaretracking.Software,
                SoftwareAction = softwaretracking.SoftwareAction,
                SoftwareActionId = softwaretracking.SoftwareActionId,
                SoftwareId = softwaretracking.SoftwareId,
                EnteredDate = softwareTrack.EnteredDate
            };
            db.Entry(softwareTrack).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        GeneratePageData(softwaretracking.Software.Id);
        return View(softwaretracking);
    }

有没有更好的选择？还是应该继续以这种方式创建视图模型？

编辑

我的业务逻辑和视图

    private void GeneratePageData(int? id = null)
    {
        ViewBag.Computers = new SelectList(db.Computers, "Id", "ComputerName");
        ViewBag.SoftwareActions = new SelectList(db.SoftwareActions, "Id", "ActionPerformed");
        var usedSoft = (from softTrack in db.SoftwareTrackings
                        where (softTrack.SoftwareActionId != 3)
                        select softTrack.Software);
        var softwareList = (from soft in db.Softwares
                            where (
                                ((from softTrack in db.SoftwareTrackings
                                  where (softTrack.SoftwareActionId != 3 && softTrack.SoftwareId == soft.Id)
                                  select softTrack.Software).Count() < soft.KeyQuantity)
                                && !(soft.AssetStatusId == 4 || soft.AssetStatusId == 5)
                                || soft.Id == id)
                            select soft).ToList();
        ViewBag.SoftwareList = softwareList.Select(t => new SelectListItem
        {
            Text = t.SoftwareIdNameFull,
            Value = t.Id.ToString()
        });
    }

而我的观点

@model Lighthouse_Asset_Manager.Models.EditSoftwareTrackingViewModel
@{
    ViewBag.Title = "Edit Software Install";
    Layout = "";
}
<div class="modal-header">
    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">
        &times;
    </button>
    <h4 class="modal-title" id="myModalLabel">Edit Software Install</h4>
</div>
<div class="modal-body">
    @using (Html.BeginForm(null, null, FormMethod.Post, new { id = "computerForm" }))
    {
        @Html.AntiForgeryToken()
        @Html.HiddenFor(model => model.Id)
        <div class="form-horizontal">
            @Html.ValidationSummary(true)

            <div class="form-group">
                @Html.LabelFor(model => model.SoftwareId, "Software", new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownList("SoftwareId", (IEnumerable<SelectListItem>)ViewBag.SoftwareList, "-- Select --", new
                    {
                        @style = "width:100%",
                        @class = "select2"
                    })
                    @Html.ValidationMessageFor(model => model.SoftwareId)
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.ComputerId, "Computer", new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownList("ComputerId", (IEnumerable<SelectListItem>)ViewBag.Computers, "-- Select --", new
                    {
                        @style = "width:100%",
                        @class = "select2"
                    })
                    @Html.ValidationMessageFor(model => model.ComputerId)
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.SoftwareActionId, "Action", new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.DropDownList("SoftwareActionId", (IEnumerable<SelectListItem>)ViewBag.SoftwareActions, "-- Select --", new
                    {
                        @style = "width:100%",
                        @class = "form-control"
                    })
                    @Html.ValidationMessageFor(model => model.SoftwareActionId)
                </div>
            </div>

            <div class="form-actions no-color">
                <button type="submit" class="btn btn-primary btn-sm"><i class="fa fa-floppy-o"></i> Edit Install Record</button>
                <button type="button" class="btn btn-default" data-dismiss="modal">
                    Cancel
                </button>
            </div>
        </div>
    }
</div>

使用视图模型的方法很好。此问题的答案解释了一些好处，包括防止过度发布攻击、使用特定于视图的显示和验证属性以及包括特定于视图的属性（如 SelectLists ）。自动映射器等工具可以轻松地在数据和视图模型之间进行映射，并减少控制器中的代码。我建议对您的视图模型进行一些更改。LastModified、Computer、Software 和 SoftwareAction 属性不是必需的（您不绑定到这些属性），我会在模型中包含SelectList属性而不是 ViewBag

查看模型

public class EditSoftwareTrackingViewModel 
{
  public int Id { get; set; }
  [Display(Name="Software")]
  public int SoftwareId { get; set; }
  [Display(Name="Computer")]
  public int ComputerId { get; set; }
  [Display(Name="Software Action")]
  public int SoftwareActionId { get; set; }
  public SelectList Computers { get; set; }
  public SelectList SoftwareActions{ get; set; }
  public SelectList SoftwareList{ get; set; }
}

然后更改GeneratePageData()方法以接受视图模型

private void GeneratePageData(EditSoftwareTrackingViewModel model)
{
  model.Computers = new SelectList(db.Computers, "Id", "ComputerName");
  ....

在视图中（始终最好使用强类型帮助程序）

@Html.DropDownListFor(m => m.SoftwareId, Model.SoftwareList, "-- Select --", new { @class = "select2" })

还有其他一些需要注意的事情。

  • 您应该使用 [Display(Name="..")] 属性（而不是 [DisplayName(..)] ）
  • 设置 LastModified 属性时，应考虑使用 UCT时间。
  • 视图中不需要 Id 属性的隐藏输入（假设您使用默认{controller}/{action}/{id}路由映射） - 它已添加到路由值中，无论如何都会绑定
  • 除非您特别想要表单的 id 属性，否则您可以只需使用@using(Html.BeginForm()) {
  • 您不需要LabelFor()中的第二个参数 - 它可以只是 Html.LabelFor(m => m.SoftwareId, new { @class = "control-label col-md-2" })，因为您已在[Display]中指定了它属性

最后，如果您想进一步简化视图，您可以考虑本答案中指示的自定义EditorTemplates或 html 帮助程序，这将允许您替换

<div class="form-group">
  @Html.LabelFor(model => model.SoftwareId, new { @class = "control-label col-md-2" })
  <div class="col-md-10">
    @Html.DropDownListFor(m => m.SoftwareId, Model.SoftwareList, "-- Select --", new { @class = "select2" })
    @Html.ValidationMessageFor(model => model.SoftwareId)
  </div>
</div>

带（自定义EditorTemplate）

@Html.EditorFor(m => m.SoftwareId, "BootstrapSelect", Model.SoftwareList)

或（自定义HtmlHelper）

@Html.BootstrapDropDownFor(m => m.SoftwareId, Model.SoftwareList)

您应该使用自动映射器使模型和视图模型之间的映射更清晰。使用此代码首先创建映射器。

Mapper.CreateMap<SoftwareTracking, EditSoftwareTrackingViewModel>();
Mapper.CreateMap<EditSoftwareTrackingViewModel, SoftwareTracking>();

如果要从模型创建视图模型，请执行以下操作：

public ActionResult Edit(int? id)
{
    SoftwareTracking tracking = db.SoftwareTrackings.Find(id);
    EditSoftwareTrackingViewModel viewmodel = 
        Mapper.Map<SoftwareTracking, EditSoftwareTrackingViewModel>(tracking);
    return View(viewmodel);
}

如果要将信息从视图模型填充回模型，请执行以下操作

public ActionResult Edit(EditSoftwareTrackingViewModel vm)
{
    if (ModelState.IsValid)
    {
        vm.LastModified = DateTime.Now;
        var softwareTrack = db.SoftwareTrackings.Find(softwaretracking.Id);
        softwareTrack = 
           Mapper.Map<EditSoftwareTrackingViewModel, SoftwareTracking>(vm, softwareTrack);
        db.Entry(softwareTrack).State = EntityState.Modified;
        db.SaveChanges();
        return RedirectToAction("Index");
    }

要在不从 DB 加载对象的情况下修补更新模型，请尝试附加：

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Edit(EditSoftwareTrackingViewModel softwaretracking)
    {
        if (ModelState.IsValid)
        {
            var softwareTrack = new SoftwareTracking
            {
                 Computer = softwaretracking.Computer,
                 ComputerId = softwaretracking.ComputerId,
                 LastModified = softwaretracking.LastModified,
                 Software = softwaretracking.Software,
                 SoftwareAction = softwaretracking.SoftwareAction,
                 SoftwareActionId = softwaretracking.SoftwareActionId,
                 SoftwareId = softwaretracking.SoftwareId,
                 EnteredDate = softwareTrack.EnteredDate
            };
            db.SoftwareTrackings.Attach(softwareTrack);
            db.Entry(softwareTrack).Property(a => a.Computer).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.ComputerId).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.LastModified).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.Computer).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.Software).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.SoftwareAction).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.SoftwareActionId).IsModified = true;
            db.Entry(softwareTrack).Property(a => a.SoftwareId).IsModified = true;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        GeneratePageData(softwaretracking.Software.Id);
        return View(softwaretracking);
    }

关于第二个问题，是使用ViewModel还是直接使用模型。这实际上是一个意见问题，每种方法都有其优点和缺点。我对此没有强烈的看法，我只想指出这些利弊供您考虑：

  • 直接使用该模型可以节省我们创建 viewModel 的过程，从而产生更小的源代码并避免映射逻辑，但它会混合问题。由于对域逻辑和与客户端通信使用相同的模型，因此如果我们不考虑这一点，对模型的任何更改都可能会传播到客户端。
  • 使用 viewModel 是分离关注点的好方法，但它需要更多的努力和映射逻辑（可能会稍微降低性能）。为了有效地应用 ViewModel，我建议使用映射器：https://github.com/AutoMapper/AutoMapper/wiki/Getting-started
这是

模型类

[Table("CURRENCY")]
    public class CurrencyClass : ICurrency
    {
        private Int32 mCURRENCY_ID = default(Int32);
        [Key]
        public virtual Int32 CURRENCY_ID  
        {
            get { return mCURRENCY_ID; }
            set { mCURRENCY_ID = value; }
        }
        private string mCURRENCY_NAME = default(string); 
        public virtual string CURRENCY_NAME 
        { 
            get { return mCURRENCY_NAME;}
            set { mCURRENCY_NAME = value;}
        }
        private string mCURRENCY_DESC = default(string);
        public  virtual string CURRENCY_DESC 
        {
            get { return mCURRENCY_DESC; }
            set { mCURRENCY_DESC = value; }
        }
        private string mCURRENCY_SYMBOLE = default(string);
        public virtual string CURRENCY_SYMBOLE 
        {
            get { return mCURRENCY_SYMBOLE; }
            set { mCURRENCY_SYMBOLE = value; }
        }
        private Int32 mcreated_by = default(Int32);
        public virtual Int32 created_by 
        {
            get { return mcreated_by; }
            set { mcreated_by = value; } 
        }
        private DateTime mcreated_date = default(DateTime);
        public virtual DateTime created_date 
        {
            get { return mcreated_date; }
            set { mcreated_date = value; } 
        }
        private Int32 mmodified_by = default(Int32);
        public virtual Int32 modified_by 
        {
            get { return mmodified_by; }
            set { mmodified_by = value; } 
        }
        private DateTime mmodified_date = default(DateTime);
        public virtual DateTime modified_date 
        {
            get { return mmodified_date; }
            set { mmodified_date = value; }
        }
    }

这是视图模型

public class CurrencyViewModel
    {
        [Key]
        public Int32 CURRENCY_Id { get; set; }
        [Required(ErrorMessage="Currency Name is required")]
        public string CURRENCY_NAME { get; set; }
        [Required(ErrorMessage="Currency Description is required")]
        public string CURRENCY_DESC { get; set; }
        [Required(ErrorMessage = "Currency Symbole is Required")]
        public string CURRENCY_SYMBOLE { get; set; }
    }

这是行动

[HttpPost]
        [ActionName("Create")]
        public ActionResult Create(CurrencyViewModel vm)
        {
            if (!ModelState.IsValid)
            {
                return View("Create");
            }   
            obj.CURRENCY_NAME = vm.CURRENCY_NAME;
            obj.CURRENCY_DESC = vm.CURRENCY_DESC;
            obj.CURRENCY_SYMBOLE = vm.CURRENCY_SYMBOLE;
            obj.created_by = 1;
            obj.created_date = DateTime.Now;
            obj.modified_by = 1;
            obj.modified_date = DateTime.Now;
            db.Currencies.Add(obj);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

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