c# - 以mvc形式上传

Question

我有一个简单的问题。为什么在下面的代码中，这部分 - HttpPostedFileBase file - 为空？当然ArticleModel模型不是null，只是file。

我的 Controller Action 开始:

public ActionResult Add(ArticleModel model, HttpPostedFileBase file)
...

我的表格:

<section id="">
@using (Html.BeginForm()) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary()
    @ViewBag.Status


    <fieldset>
        <legend>Add</legend>
        <ol>
            <li>
                @Html.LabelFor(m => m.title)
                @Html.TextBoxFor(m => m.title)
            </li>
            <li>
                @Html.LabelFor(m => m.Categories)
                @Html.DropDownListFor(m=> m.categoryID, Model.Categories, "- lorem -", new { @class="dropdownlist" })
            </li>
            <li>
                @Html.LabelFor(m => m.connectedArticlesID)
                @Html.TextBoxFor(m => m.connectedArticlesID)
            </li>
            <li>
                 <input type="file" name="file" id="file" />
            </li>
            <li>
                @Html.LabelFor(m => m.introduction)
                @Html.EditorFor(m => m.introduction)
            </li>
            <li>
                @Html.LabelFor(m => m.content)
                @Html.EditorFor(m => m.content)
            </li>
        </ol>
        <input type="submit" value="Add" />
    </fieldset>
}
</section>

编辑:

我的模型

public class ArticleModel
{
    [Display(Name = "Number")]
    public int articleID { get; set; }

    [Required]
    [Display(Name = "Tilte")]
    [StringLength(250, ErrorMessage = "Tytuł musi mieć długość od {0} do {2} znaków.", MinimumLength = 6)]
    public string title { get; set; }

    [Required]
    [Display(Name = "Similar articles")]
    public string connectedArticlesID { get; set; }

    [Display(Name = "CategoryName")]
    public string category { get; set; }

    [Required]
    [Display(Name = "Category")]
    public int categoryID { get; set; }

    [Required]
    [Display(Name = "Category")]
    public IEnumerable<SelectListItem> Categories
    {
        get
        {
            return new[]
            {
                new SelectListItem { Value = "1", Text = "Kategoria pierwsza" },
                new SelectListItem { Value = "2", Text = "Kategoria druga" },
                new SelectListItem { Value = "3", Text = "Kategoria trzecia" },
            };
        }
    }

    [Display(Name = "Content")]
    [Required]
    [StringLength(6000, ErrorMessage = "Treść musi mieć długość od {1} do {2} znaków.", MinimumLength = 30)]
    [UIHint("tinymce_jquery_full"), AllowHtml]
    public string content { get; set; }

    [Display(Name = "Introduction")]
    [Required]
    [StringLength(6000, ErrorMessage = "Wstęp musi mieć długość od {1} do {2} znaków.", MinimumLength = 30)]
    [DataType(DataType.MultilineText)]
    public string introduction { get; set; }
}

Answer 1

I have a simple question. Why in code below, this part - HttpPostedFileBase file - is null?

因为您没有在表单上将 enctype 设置为 multipart/form-data:

@using (Html.BeginForm(null, null, FormMethod.Post, new { enctype = "multipart/form-data" })) 
{
    ...
}

引用:http://haacked.com/archive/2010/07/16/uploading-files-with-aspnetmvc.aspx

在将 Html.BeginForm 切换为 Ajax.BeginForm 然后问一个问题为什么 HttpPostedFileBase 文件 - 为空之前，答案是您不能使用 AJAX 上传文件。您将不得不使用文件上传插件，例如 Uploadify 或 Blueimp 文件上传。我只是为了记录而提及这一点，以避免进一步可能出现的重复问题。

---

更新:

根据评论部分的要求，您可以将文件字段添加到您的 View 模型中:

public class ArticleModel
{
    [Required]
    public HttpPostedFileBase File { get; set; }

    ...
}

然后让您的 Controller 操作直接将此 View 模型作为参数并摆脱 HttpPostedFileBase 参数:

public ActionResult Add(ArticleModel model)
{
    if (ModelState.IsValid)
    {
        ... work with model.File directly here
    }
}

同时为了避免域模型和 View 模型之间的任何歧义，我会在它们后面加上 ViewModel:

public class ArticleViewModel
{
    ...
}