I get the following error when trying to run my application:
传递到字典中的模型项的类型为“System.Linq.GroupedEnumerable'3 [WebApplication1.Question，System.Int32，WebApplication1.Question]”，但此字典需要类型为“System.Collections”的模型项。 Generic.IEnumerable`1 [WebApplication1.Question]”。
这是堆栈跟踪：
[InvalidOperationException: The model item passed into the dictionary is of type 'System.Linq.GroupedEnumerable`3[WebApplication1.Question,System.Int32,WebApplication1.Question]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[WebApplication1.Question]'.]
System.Web.Mvc.ViewDataDictionary`1.SetModel(Object value) +175
System.Web.Mvc.ViewDataDictionary..ctor(ViewDataDictionary dictionary) +107
System.Web.Mvc.WebViewPage`1.SetViewData(ViewDataDictionary viewData) +49
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +99
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +291
System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +56
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +52
System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +173
System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +100
System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +13
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +36
System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +12
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +22
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +21
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9765901
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155
和我的问题控制器：
// GET: Questions
public ActionResult Index()
{
var questions = db.Questions.Include(q => q.Step);
return View(questions.ToList().GroupBy(x=>x.idStep));
}
// GET: Questions/Details/5
public ActionResult Details(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Question question = db.Questions.Find(id);
if (question == null)
{
return HttpNotFound();
}
return View(question);
}
// GET: Questions/Create
public ActionResult Create()
{
ViewBag.idStep = new SelectList(db.Steps, "idStep", "nameStep");
return View();
}
// POST: Questions/Create
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see http://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "idQuestion,idStep,Question1")] Question question)
{
if (ModelState.IsValid)
{
db.Questions.Add(question);
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.idStep = new SelectList(db.Steps, "idStep", "nameStep", question.idStep);
return View(question);
}
// GET: Questions/Edit/5
public ActionResult Edit(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Question question = db.Questions.Find(id);
if (question == null)
{
return HttpNotFound();
}
ViewBag.idStep = new SelectList(db.Steps, "idStep", "nameStep", question.idStep);
return View(question);
}
// POST: Questions/Edit/5
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see http://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit([Bind(Include = "idQuestion,idStep,Question1")] Question question)
{
if (ModelState.IsValid)
{
db.Entry(question).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.idStep = new SelectList(db.Steps, "idStep", "nameStep", question.idStep);
return View(question);
}
// GET: Questions/Delete/5
public ActionResult Delete(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Question question = db.Questions.Find(id);
if (question == null)
{
return HttpNotFound();
}
return View(question);
}
// POST: Questions/Delete/5
[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public ActionResult DeleteConfirmed(int id)
{
Question question = db.Questions.Find(id);
db.Questions.Remove(question);
db.SaveChanges();
return RedirectToAction("Index");
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
db.Dispose();
}
base.Dispose(disposing);
}
}
}
和我的观点：
@model IEnumerable<WebApplication1.Question>
@{
ViewBag.Title = "Index";
}
<h2>Index</h2>
<p>
@Html.ActionLink("Create New", "Create")
</p>
<table class="table">
<tr>
<th>
</th>
<th>
@Html.DisplayNameFor(model => model.Step.nameStep)
</th>
<th>
@Html.DisplayNameFor(model => model.Question1)
</th>
<th></th>
</tr>
@foreach (var item in Model) {
<tr>
<td>
@Html.ActionLink("Edit", "Edit", new { id = item.idQuestion }) |
@Html.ActionLink("Details", "Details", new { id = item.idQuestion }) |
@Html.ActionLink("Delete", "Delete", new { id = item.idQuestion })
</td>
<td>
@Html.DisplayFor(modelItem => item.Step.nameStep)
</td>
<td>
@Html.DisplayFor(modelItem => item.Question1)
</td>
</tr>
}
</table>
答案 0 :(得分：1)
问题源于您使用以下代码返回视图页面的方式：
return View(questions.ToList().GroupBy(x => x.idStep));
GroupBy LINQ方法生成GroupedEnumerable作为结果（而不是IEnumerable），因为您的模型需要IEnumerable指令给出的@model集合，除非使用返回GroupedEnumerable的方法，即IEnumerable，否则无法从IEnumerable直接转换为ToList。
尝试在GroupBy之前使用ToList，如下所示，以便您的操作方法返回实现List<Question>的{{1}}：
IEnumerable注意：如果您不确定在public ActionResult Index()
{
var questions = db.Questions.Include(q => q.Step).GroupBy(x => x.idStep).ToList();
return View(questions);
}
之后直接放置GroupBy，请在开始分组之前使用Include将联接查询转换为集合。