在我的MVC网络应用程序中，我试图在向数据库提交新记录时上传文件，但每当发生这种情况时，我都会收到“对象引用未设置为对象上的实例”错误。以下是我的模型：
public class MenteeViewModel
{
public mentee mentee { get; set; }
public guardian guardian { get; set; }
public address address { get; set; }
public email email { get; set; }
public user users { get; set; }
public phnumber phnumber { get; set; }
public econtact econtact { get; set; }
[Display(Name = "School System")]
public int SelectedSSystemId { get; set; }
public IEnumerable<SelectListItem> SSystemItems { get; set; }
[Display(Name = "School")]
public int SelectedSchoolId { get; set; }
public IEnumerable<SelectListItem> SchoolItems { get; set; }
public ssystem ssystems { get; set; }
public school schools{ get; set; }
//This is for UPLOADING image and inserting image information to database
public HttpPostedFileBase File { get; set; }
public image image { get; set; }
}
以下是我实际尝试上传文件的控制器代码部分：
[HttpPost]
public ActionResult Create(MenteeViewModel menteeViewModel, HttpPostedFileBase file )
{
if (ModelState.IsValid)
{
var regModel = new RegisterModel();
try
{
DateTime now = DateTime.Now;
menteeViewModel.address.CreatedOn = now;
menteeViewModel.guardian.CreatedOn = now;
menteeViewModel.econtact.CreatedOn = now;
menteeViewModel.email.CreatedOn = now;
menteeViewModel.phnumber.CreatedOn = now;
menteeViewModel.mentee.addresses.Add(menteeViewModel.address);
menteeViewModel.mentee.guardians.Add(menteeViewModel.guardian);
menteeViewModel.mentee.econtacts.Add(menteeViewModel.econtact);
menteeViewModel.mentee.emails.Add(menteeViewModel.email);
menteeViewModel.mentee.phnumbers.Add(menteeViewModel.phnumber);
Regex pattern = new Regex("[-/]");
var strDob = (DateTime) menteeViewModel.mentee.dob;
var newDate = strDob.ToShortDateString();
newDate = pattern.Replace(newDate, "");
regModel.UserName = menteeViewModel.email.email_address;
regModel.Password = newDate;
WebSecurity.CreateUserAndAccount(regModel.UserName, regModel.Password);
Roles.AddUsersToRole(new[] {regModel.UserName}, "User");
menteeViewModel.mentee.active_flag = "N";
menteeViewModel.mentee.flag3 = menteeViewModel.schools.school_id.ToString();
menteeViewModel.mentee.CreatedOn = now;
var vfileName = Guid.NewGuid().ToString() + Path.GetFileName(menteeViewModel.image.image_path);
var path = Path.Combine(Server.MapPath("~/App_Data"), vfileName);
menteeViewModel.File.SaveAs(path);
menteeViewModel.image.image_path = path;
menteeViewModel.mentee.images.Add(menteeViewModel.image);
db.mentees.Add(menteeViewModel.mentee);
db.SaveChanges();
}
catch (DbEntityValidationException e)
{
foreach (var eve in e.EntityValidationErrors)
{
Console.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
eve.Entry.Entity.GetType().Name, eve.Entry.State);
foreach (var ve in eve.ValidationErrors)
{
Console.WriteLine(" - Property: \"{0}\", Error: \"{1}",
ve.PropertyName, ve.ErrorMessage);
}
}
throw;
}
return RedirectToAction("Index");
}
return Create();
}
以下是视图：
BEMentoring.ViewModels.MenteeViewModel
@{
ViewBag.Title = "Create";
}
<h2>Create</h2>
@using (Html.BeginForm()) {
@Html.ValidationSummary(true)
<fieldset>
<legend>MenteeViewModel</legend>
<div class="editor-label">
@Html.LabelFor(model => model.mentee.first_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.mentee.first_name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.mentee.middle_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.mentee.middle_name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.mentee.last_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.mentee.last_name)
</div>
<!-- Gender, DOB, Class Grade !-->
<div class="editor-label">
@Html.LabelFor(model => model.mentee.gender)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.mentee.gender)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.mentee.dob)
</div>
<div class="editor-field">
@Html.JQueryUI().DatepickerFor(model => model.mentee.dob).ChangeYear(new YearDefinition(-20, RelativeTo.SelectedYear), new YearDefinition(2012)).DateFormat("yyyy-mm-dd")
</div>
<div class="editor-label">
@Html.LabelFor(model => model.mentee.class_grade)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.mentee.class_grade)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.address.address1)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.address.address1)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.address.city)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.address.city)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.address.state)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.address.state)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.ssystems.ssystem_id)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.ssystems.ssystem_id, new SelectList(ViewBag.SSystems as System.Collections.IEnumerable, "ssystem_id","ssystem_name"),
"--Select One--", new {id = "ddlSystem"})
</div>
<div class="editor-label">
@Html.LabelFor(model => model.schools.school_id)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.schools.school_id, new SelectList(ViewBag.Schools as System.Collections.IEnumerable, "school_id","school_name"),
"--Select One--", new {id = "ddlSchool"})
</div>
<div class="editor-label">
@Html.LabelFor(mode => Model.econtact.first_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.econtact.first_name)
</div>
<div class="editor-label">
@Html.LabelFor(mode => Model.econtact.last_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.econtact.last_name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.econtact.phone)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.econtact.phone)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.email.email_address)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.email.email_address)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.phnumber.area_code)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.phnumber.area_code)
@Html.EditorFor(model => model.phnumber.phone)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.guardian.first_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.guardian.first_name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.guardian.middle_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.guardian.middle_name)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.guardian.last_name)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.guardian.last_name)
</div>
<div>
@Html.LabelFor(model => model.File)
@Html.TextBoxFor(model => model.image.image_path, new {type = "file"})
</div>
<p>
<input type="submit" value="Create" />
</p>
</fieldset>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
@Scripts.Render("~/bundles/jqueryui")
我已经搜索过，但未能找到这个问题的有用答案。如果有一个可以帮助我，我错过了请帮助！提前致谢
答案 0 :(得分：1)
你这样做：
<div>
@Html.LabelFor(model => model.File)
@Html.TextBoxFor(model => model.image.image_path, new {type = "file"})
</div>
将其改为：
<div>
@Html.LabelFor(model => model.File)
<input name="file" type="file">
</div>
这应映射到您的viewmodel File属性。顺便说一句，这个名字并不是最好的...但它应该有效。
在您的控制器中，您接收已发布的文件作为参数...而不是模型本身...所以您需要从该参数中获取它。
答案 1 :(得分：0)
使用HttpPostedFileBase file参数处理文件。我发现您发布的代码中缺少边界检查。请务必检查null，其中对象可以为null，如本例所示。