asp.net-mvc-4 - 在 ASP.NET MVC 4 中填充和选择下拉列表值

Question

ASP.NET MVC 中的下拉列表让我感到困惑。我有一个模特类。模型类有一个名为 SelectedValue 的字符串。该字符串代表先前选择的值。我有一个从数据库中提取的项目集合。集合中的每个项目都有一个 ID 和一个名称值。我的问题是，我不知道将此信息输入 UI 的推荐方法是什么。

我不确定是否应该使用 ViewBag 还是 Model。但一旦该值存在，我什至不确定填充 UI 的最佳方法是什么。我见过 HTML 助手和使用 RAZOR 语法的人。我很困惑。人们推荐什么？

谢谢

Answer 1

这就是我的做法，假设你有 2 个模型团队和玩家:

Player.cs

public class Player
{
    [HiddenInput(DisplayValue = false)]
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }        

    [Required]
    [ForeignKey("Team")]
    [Display(Name = "Team")]
    public int TeamId { get; set; }        

    [Display(Name = "First name")]
    public string FirstName { get; set; }

    [Display(Name = "Last name")]
    public string LastName { get; set; }

    public virtual Team Team { get; set; }        
}

Team.cs

 public class Team
{
    [Key]
    [HiddenInput(DisplayValue = false)]
    public int TeamId { get; set; }

    [Display(Name = "Full Name:")]
    public string Name { get; set; }        

    public virtual ICollection<Player> Players { get; set; }
}

然后在你的 PlayerController 中: 注意:团队需要存在才能创建玩家

    private void PopulateTeamsDropDownList(object selectedTeams = null)
    {
        var teamsQuery = from d in _dataSource.Teams
                         orderby d.Name
                         select d;
        ViewBag.TeamID = new SelectList(teamsQuery, "TeamId", "Name", selectedTeams);
    }

    [HttpGet]
    public ActionResult Create()
    {
        PopulateTeamsDropDownList();
        return View();
    }

    [HttpPost]
    public ActionResult Create(Player model)
    {
        if (ModelState.IsValid)
        {
            using (EFootballDb db = new EFootballDb())
            {
                try
                {
                    var player = new Player
                                     {
                                         FirstName = model.FirstName,
                                         LastName = model.LastName
                                     };
                    db.Players.Add(player);
                    db.SaveChanges();
                    return RedirectToAction("About", "Home");
                }
                catch (Exception)
                {
                    ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists, see your system administrator.");
                }
            }
        }
        PopulateTeamsDropDownList(model.TeamId);
        return View(model);
    }

最后，您的“为播放器创建 View ”将如下所示:

@{
ViewBag.Title = "Create";
 }

<h2>Create</h2>

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

<fieldset>
    <legend>Player</legend>

    <div class="editor-label">
            @Html.LabelFor(model => model.TeamId, "Pick Your Team")
    </div>
    <div class="editor-field">
        @Html.DropDownList("TeamId", String.Empty)
        @Html.ValidationMessageFor(model => model.TeamId)
    </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>        

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

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

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