Question

我有一个控制器，其中我有Create方法。我的目标是上传图片以及特定人员所涉及的名称和服务。我的代码非常好。但是我遇到错误'对象引用未设置为控制器中的一个对象'在'行'if（leader.File.ContentLength＆gt;（2 * 1024 * 1024））'的实例。代码非常好。请让我知道我在哪里做错了

我有这样的模型类：

   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int ID { get; set; }

   [Required(ErrorMessage="The Name is required")] 
   [MaxLength(20,ErrorMessage="The Maximum characters allowed is 20")]
   [MinLength(4,ErrorMessage="The Minimum charcaters allowed is 4")]
   public string Name { get; set; }

   [Required(ErrorMessage="Picture is required")]
   public byte[] Picture { get; set; }

   public int ImageSize { get; set; }

   [NotMapped]
   public HttpPostedFileBase File { get; set; }

   public int MinistryID { get; set; }

   [ForeignKey("MinistryID")]
   public virtual Ministry Ministry { get; set; }

我有一个带有这样的create方法的Controller类：

   public ActionResult Create()
        {

            return View();
        }
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create(Leader leader)
        {
            if (leader.File.ContentLength > (2 * 1024 * 1024))
            {
                ModelState.AddModelError("CustomError", "File size must be
             less than 2 MB");
                return View();
            }
            if (!(leader.File.ContentType == "image/jpeg" || 
           leader.File.ContentType == "image/gif"))
            {
                ModelState.AddModelError("CustomError", "File type allowed :
              jpeg and gif");
                return View();
            }

            leader.ImageSize = leader.File.ContentLength;

            byte[] data = new byte[leader.File.ContentLength];
            leader.File.InputStream.Read(data, 0,
            leader.File.ContentLength);

            leader.Picture = data;
           if(ModelState.IsValid)
            {
                db.Leaders.Add(leader);
                db.SaveChanges();
            }
            return View(leader);

        }
        }

Create方法的视图是：

     @model ChurchWebsite.Models.Leader

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

<h2>Create</h2>

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

    <fieldset>
        <legend>Leader</legend>

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

        <div>
            @Html.LabelFor(model=>model.Picture)
        </div>
         <div>
        @using (Html.BeginForm("Upload","Image", FormMethod.Post,new{enctype="multipart/form-data"}))
            {
            @Html.TextBoxFor(Model=> Model.File, new{type="file",enctype="multipart/form-data"})
            @Html.ValidationMessage("CustomError")
           </div>

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

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



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

Answer 1

您有嵌套的表单，这些表单是无效的html，当您单击内部表单中的提交按钮时，它将发布没有enctype="multipart/form-data"属性的外部表单，因此，文件不会被发送在控制器中，leader.File为空，访问其ContentLength属性会抛出异常。您需要删除内部嵌套表单元素并将enctype属性添加到外部表单。

你的观点应该是（不相关的html删除）

@model ChurchWebsite.Models.Leader
....
@using (Html.BeginForm("Create", YourControllerName, FormMethod.Post, new{ enctype="multipart/form-data" })) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)
    ....
    @Html.LabelFor(m => m.Name)
    @Html.EditorFor(m => m.Name)
    @Html.ValidationMessageFor(m => m.Name)
    ....
    @Html.TextBoxFor(m => m.File, new{ type="file" }) // remove the inva;id enctype attribute
    @Html.ValidationMessage("CustomError")
    ....
    @Html.LabelFor(model => model.MinistryID)
    @Html.EditorFor(model => model.MinistryID)
    @Html.ValidationMessageFor(model => model.MinistryID)
    <input type="submit" value="Create" />
}

对象引用未设置为对象的实例-mvc4

1 个答案: