我添加了代码以显示我的表格中的许多复选框（HairTags），并且在我的表单中CreationUpload.cshtml我收到以下错误：
发生了'System.NullReferenceException'类型的异常 App_Web eba142hb.dll但未在用户代码中处理 information：对象引用未设置为对象的实例。
对象引用未设置为对象的实例。
<div class="col-md-12">
@for (int i = 0; i < Model.CreationHairTags.Count; i++)
{
@Html.CheckBoxFor(m => Model.CreationHairTags[i].IsChecked)
@Model.CreationHairTags[i].Text
@Html.HiddenFor(m => Model.CreationHairTags[i].Value)
@Html.HiddenFor(m => Model.CreationHairTags[i].Text)<br />
}
</div>
这是我的模型Creation.cs（粗体添加的代码）
namespace HairCollection3.Models
{
public class Creation
{
public string UserId { get; set; }
[Key]
public int CreationId { get; set; }
[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ViewRes.ValidationStrings))]
[Display(Name = "Sex", ResourceType = typeof(ViewRes.Names))]
public string CreationSex { get; set; }
[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ViewRes.ValidationStrings))]
[Display(Name = "CreationTitle", ResourceType = typeof(ViewRes.NamesCreation))]
[StringLength(2000)]
[AllowHtml]
public string CreationTitle { get; set; }
public string CreationPhotoBis { get; set; }
public string Creationtag { get; set; }
public virtual ICollection<CreationLike> CreationLikes { get; set; }
}
public class CreationLike
{
public int CreationId { get; set; }
public string UserId { get; set; }
public virtual ApplicationUser User { get; set; }
[Key]
public int CreationLikeId { get; set; }
public virtual Creation ParentCreation { get; set; }
}
public class HairTag
{
[Key]
public int HairTagId { get; set; }
[Required]
public string HairTagTitle { get; set; }
[Required]
public string HairTagType { get; set; }
[Required]
public int HairTagOrder { get; set; }
}
***//CHECKBOXES
public class HairTagModel
{
[Key]
public int Value { get; set; }
public string Text { get; set; }
public bool IsChecked { get; set; }
}
public class HairTagList
{
private ApplicationDbContext creationdb = new ApplicationDbContext();
public HairTagList()
{
var HairTagList = creationdb.HairTags.ToList();
List<HairTagModel> obj = new List<HairTagModel>();
foreach (var tags in HairTagList)
{
obj.Add(new HairTagModel
{
Text = tags.HairTagTitle,
Value = tags.HairTagId,
IsChecked = false
});
}
this.CreationHairTags = obj;
}
public List<HairTagModel> CreationHairTags { get; set; }
//public List<HairTagModel> ListHairTags { get; set; }
}
public class CreationHairTagsModel
{
public Creation Creation { get; set; }
public List<HairTagModel> CreationHairTags { get; set; }
}
}***
我的控制器CreationController.cs
// GET: /Creation/CreationUpload
[Authorize]
public ActionResult CreationUpload()
{
CreationHairTagsModel creation = new CreationHairTagsModel();
return View(creation);
//return View();
}
// POST: /Creation/CreationUpload
// Afin de déjouer les attaques par sur-validation, activez les propriétés spécifiques que vous voulez lier. Pour
// plus de détails, voir http://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[Authorize]
[ValidateAntiForgeryToken]
public ActionResult CreationUpload([Bind(Include = "CreationId,CreationSex,CreationTitle,CreationPhotoBis,CreationHairTags")] CreationHairTagsModel creation, IEnumerable<HttpPostedFileBase> files)
{
if (ModelState.IsValid)
{
// update each field manually
foreach (var file in files)
{
if (file != null)
{
if (file.ContentLength > 0)
{
....CODE UPLOAD HIDDEN....
//Avoid Script
var CreationTitletocheck = Regex.Replace(creation.Creation.CreationTitle, @"<script\b[^<]*(?:(?!<\/script>)<[^<]*)*<\/script>", string.Empty);
CreationTitletocheck = Regex.Replace(CreationTitletocheck, @"(?></?\w+)(?>(?:[^>'""]+|'[^']*'|""[^""]*"")*)>", string.Empty);
creation.Creation.CreationTitle = CreationTitletocheck;
//Tags
StringBuilder sb = new StringBuilder();
foreach (var item in creation.CreationHairTags)
{
if (item.IsChecked)
{
sb.Append(item.Text + ",");
}
}
creation.Creation.Creationtag = sb.ToString();
creation.Creation.UserId = User.Identity.GetUserId();
db.Creations.Add(creation.Creation);
db.SaveChanges();
}
}
}
}
//UserId
return RedirectToAction("CreationList", "Creation", new { UserId = User.Identity.GetUserId() });
}
return View(creation);
}
我的上传CreationUpload.cshtml页面
@model HairCollection3.Models.CreationHairTagsModel
@using Microsoft.AspNet.Identity
@{
ViewBag.Title = ViewRes.NamesCreation.CreationUploadTitle;
}
<div class="col-sm-12 col-md-12 chpagetop">
<h1>@ViewRes.Shared.PublishAPhoto</h1>
<hr />
@using (Html.BeginForm("CreationUpload", "Creation", FormMethod.Post, new { id = "CreationUpload", enctype = "multipart/form-data", onsubmit = "$('#creationloading').show(); $('#creationform').hide();" }))
{
@Html.AntiForgeryToken()
<div class="col-md-12" id="creationloading" style="display:none">
<div id="progress">
<p>@ViewRes.Shared.UploadPhotoProgress<strong>0%</strong></p>
<progress value="5" min="0" max="100"><span></span></progress>
</div>
</div>
<div class="col-md-12" id="creationform">
<div class="col-md-12">
@Html.ValidationMessageFor(m => m.Creation.CreationSex)
@Html.RadioButtonFor(m => m.Creation.CreationSex, "F", new { @checked = true }) @ViewRes.Shared.WomanHairstyle @Html.RadioButtonFor(m => m.Creation.CreationSex, "M") @ViewRes.Shared.ManHairstyle
</div>
<div class="col-md-12">
@Html.ValidationMessageFor(m => m.Creation.CreationTitle)
@Html.TextBoxFor(m => m.Creation.CreationTitle, new { @class = "inputplaceholderviolet wid100x100", placeholder = HttpUtility.HtmlDecode(Html.DisplayNameFor(m => m.Creation.CreationTitle).ToHtmlString()), onfocus = "this.placeholder = ''", onblur = "this.placeholder = '" + HttpUtility.HtmlDecode(Html.DisplayNameFor(m => m.Creation.CreationTitle).ToHtmlString()) + "'" })
</div>
<div class="col-md-12">
@for (int i = 0; i < Model.CreationHairTags.Count; i++)
{
@Html.CheckBoxFor(m => Model.CreationHairTags[i].IsChecked)
@Model.CreationHairTags[i].Text
@Html.HiddenFor(m => Model.CreationHairTags[i].Value)
@Html.HiddenFor(m => Model.CreationHairTags[i].Text)<br />
}
</div>
<div class="col-md-12" style="text-align: center">
<p style="display: inline-block">
<input type="file" accept="image/*" onchange="loadFile(event)" name="files" id="file1" translate="yes" data-val="true" data-val-required="A File is required." class="wid100x100" /><label for="file1"></label>
<img id="output" style="max-width:200px;"/>
</p>
</div>
<div class="col-sm-12 col-md-12 chpagetopdiv">
<button type="submit" title="@ViewRes.Shared.Publish"><span class="glyphicon glyphicon-share-alt"></span> @ViewRes.Shared.Publish</button>
</div>
</div>
}
</div>
我的代码有什么问题请帮忙解释一下？
答案 0 :(得分：0)
重要提示： 在C＃中，每个集合必须在被访问之前进行初始化
当您尝试从View访问CreationHairTags集合时，会发生错误，该集合未初始化。替换模型以在类构造函数中初始化集合：
public class CreationHairTagsModel
{
public Creation Creation { get; set; }
public List<HairTagModel> CreationHairTags { get; set; }
public CreationHairTagsModel()
{
CreationHairTags = new List<HairTagModel>();
}
}