Question

我正在尝试使用具有一对多关系的实体框架创建ASP.NET MVC应用程序。为此我已成功设法将相应的项目列表加载到下拉控件（在“创建”视图中），但是当我单击“创建”按钮（在“创建”视图中）页面验证为faild时，验证错误消息为The value '1' is invalid.。

错误

模型

public class Post
{
    public int Id { get; set; }
    ...
    public virtual Person Author { get; set; }
}

DataBaseContext

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
    modelBuilder.Entity<Post>()
                .HasOptional(p => p.Author);
}

控制器

public ActionResult Create()
    {
        PopulateAuthorDropDownList();
        return View();
    }

    [HttpPost]
    public ActionResult Create(Post post)
    {
        if (ModelState.IsValid)
        {
            db.Posts.Add(post);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        PopulateAuthorDropDownList(post.Author);
        return View(post);
    }

    private void PopulateAuthorDropDownList(object selectedPerson = null)
    {
        var personQuery = from d in db.People
                          orderby d.Name
                          select d;
        ViewBag.Author = new SelectList(personQuery, "Id", "Name", selectedPerson);
    }

查看

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

当我在数据库中检查作者表时，会有Id 1的记录，所以我猜1是一个有效值。我在这里缺少什么？

提前致谢...

Answer 1

您没有显示Author对象的外观，

假设它是这样的，

public class Author
{ 
   public int Id{get;set;}
   public string Name{get;set;}
}

试试这个，

<div class="editor-label">
    @Html.LabelFor(model => model.Author)
</div>
<div class="editor-field">
    @Html.DropDownListFor(model => model.Author.Id, ViewBag.Author, "Select an Author")
    @Html.ValidationMessageFor(model => model.Author)
</div>

Answer 2

你应该有这样的东西：

<div class="editor-label">
    @Html.LabelFor(model => model.Author.Name)
</div>
<div class="editor-field">
    @Html.DropDownListFor(model => model.Author.Name, (SelectList)ViewBag.AuthorList)
    @Html.ValidationMessageFor(model => model.Author.Name)
</div>

请注意，您应该将ViewBag.AuthorList命名为ViewBag.Author

Answer 3

通过

管理解决此问题

将模型更改为

public class Post
{
    public int Id { get; set; }
    ...
    public int Author { get; set; } // changed type to int
}

将查看更改为

    <div class="editor-label">
        @Html.LabelFor(model => model.Author)
    </div>
    <div class="editor-field">
        @Html.DropDownList("AuthorId", String.Empty)
        @Html.ValidationMessageFor(model => model.Author)
    </div>

将控制器更改为

private void PopulateAuthorDropDownList(object selectedPerson = null)
    {
        var personQuery = from d in db.People
                          orderby d.Name
                          select d;
        ViewBag.AuthorId = new SelectList(personQuery, "Id", "UserName", selectedPerson); //Changed Author to AuthorId
    }

并删除

    modelBuilder.Entity<Post>()
                .HasOptional(p => p.Author);

来自 DataBaseContext

无论如何感谢答案......：）

Answer 4

您必须向DropDownList提供string.empty的选项列表。

我应该使用强类型版本DropDownListFor：

@Html.DropDownListFor(model => model.Author.Name, Model.AuthorList)

或者甚至可以更好地使用名称而不是Id：

@Html.DropDownListFor(model => model.Author.Id, Model.AuthorList)

你的模特：

class Model {
    ...
    public SelectList AuthorList {get;set;}
}

在你的控制器中：

model.AuthorList = new SelectList(fetchAuthors()
                         .Select(a => new SelectListItem {
                                          Text = a.Name,
                                          Value = a.Id 
                                      }, "Value", "Text");

ASP.NET MVC页面验证失败（该值无效。）

4 个答案: