如何将值从数据库映射到 MVC 4 中的视图模型

Question

我在完成一项非常简单的任务时遇到了麻烦。我正在尝试将从数据库检索到的值映射到视图模型。然后我想将它作为模型传递给我的视图。

视图模型称为 EditAdminModelVM，它包含来自称为 UserProfile 的较大类的属性的较小子集。我选择使用视图模型是因为我不希望用户能够更新整个域模型，而只更新其中的一部分。

这是视图模型：

public class EditAdminModelVM
{
    [Required]
    [StringLength(50, ErrorMessage = "The {0} must be at least {2} characters long.")]
    [Display(Name = "First name")]
    public string FirstName { get; set; }

    [Required]
    [StringLength(50, ErrorMessage = "The {0} must be at least {2} characters long.")]
    [Display(Name = "Last name")]
    public string LastName { get; set; }

    [Required]
    [MaxLength(250)]
    [EmailAddress]
    public string Email { get; set; }

    [Required]
    //[Remote("doesUserNameExist", "Account", HttpMethod = "POST", ErrorMessage = "Username already exists. Please enter a different User Name.")] //note this checks from client-side only - server side check is built in to membership
    [Display(Name = "Username")]
    public string UserName { get; set; }

    [HiddenInput]
    public int UserId { get; set; }
}

这是控制器9，虽然它不起作用）：

[Authorize(Roles = "Admin")]
    public ActionResult EditAdmin(int id = 0)
    {
        PpDB db = new PpDB();

        var viewModel = new EditAdminModelVM();

        viewModel = db.UserProfiles
             .Where(x => x.UserId == id)
             .Select(x => new EditAdminModelVM
             {
                 FirstName = x.FirstName,
                 LastName = x.LastName,
                 Email = x.Email,
                 UserName = x.UserName
             });

        return View(viewModel);
    }

在这种情况下，.Select 带有下划线，带有一个波浪线，它说明了 IQueryable 的一些内容。但是如果我尝试设置 var viewModel = new IQueryable;我收到另一个错误。

我想这可能是语法问题。这个数据库查询应该只返回一行，所以我认为 IQueryable 没有必要，但我不是专家。

如果您可以为我提供如何构建此代码块的工作示例，那么我可以通过示例学习 - 对我疲惫的大脑更好。

非常感谢！

肯更新 这是更新后的控制器：

 [Authorize(Roles = "Admin")]
    public ActionResult EditAdmin(int id = 0)
    {
        PpDB db = new PpDB();

        List<EditAdminModelVM> viewModel = new List<EditAdminModelVM>();

        viewModel = db.UserProfiles
             .Where(x => x.UserId == id)
             .Select(x => new EditAdminModelVM
             {
                 FirstName = x.FirstName,
                 LastName = x.LastName,
                 Email = x.Email,
                 UserName = x.UserName,
                 UserId = x.UserId
             }).ToList();

        return View(viewModel);
    }

这是视图：

@model List<PpModels.Models.EditAdminModelVM>


@{
    ViewBag.Title = "Edit Admin";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

@using (Html.BeginForm()) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

<fieldset>
    <legend>UserProfile</legend>

    @Html.HiddenFor(model => model.UserId)

    <div class="editor-label">
        @Html.LabelFor(model => model.UserName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.UserName)
        @Html.ValidationMessageFor(model => model.UserName)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.FirstName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.FirstName)
        @Html.ValidationMessageFor(model => model.FirstName)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.LastName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.LastName)
        @Html.ValidationMessageFor(model => model.LastName)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.Email)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.Email)
        @Html.ValidationMessageFor(model => model.Email)

    <p>
        <input type="submit" value="Save" />
    </p>
</fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

Answer 1

将var viewModel = new EditAdminModelVM(); 更改为List<EditAdminModelVM> viewModel = new List<EditAdminModelVM>(); 并将ToList() 附加到db.UserProfiles 查询的末尾。现在，这个将 EditAdminModelVM 的集合传递给您的视图。在您的视图中遍历此集合以获得所需的输出。

更新：对于单个实例：

[Authorize(Roles = "Admin")]
public ActionResult EditAdmin(int id = 0)
{
    PpDB db = new PpDB();

    var viewModel = new EditAdminModelVM();

    viewModel = db.UserProfiles
         .Where(x => x.UserId == id)
         .Select(x => new EditAdminModelVM
         {
             FirstName = x.FirstName,
             LastName = x.LastName,
             Email = x.Email,
             UserName = x.UserName
         }).FirstOrDefault();

    return View(viewModel);
}

为此，您无需在视图中进行迭代：

在您的视图中使用@model ProofPixModels.Models.EditAdminModelVM。