c# - 'IEnumerable< >' does not contain a definition for ' ' 并且找不到接受类型为 '' 的第一个参数的扩展方法 'IEnumerable<>'

Question

我想创建如下图所示的在线论坛

---

---

这是我的 Controller 方法

public ActionResult Discussion_Preview()
{

    int Discussion_ID = 1;


   var discussion_preview = (from d in db.AB_Discussion
                              where d.Discussion_ID == Discussion_ID
                              join dc in db.AB_DiscussionComments on d.Discussion_ID equals dc.Discussion_ID
                              join user_discussion in db.AspNetUsers on d.CreatedBy equals user_discussion.Id
                              join user_comments in db.AspNetUsers on dc.CreatedBy equals user_comments.Id
                              select new DiscussionPreview_Model
                              {
                                Disussion_ID = d.Discussion_ID,
                                Discussion_CreateDate = d.CreatedDate,
                                Discussion_CreateBy = user_discussion.UserName,
                                Discussion_Title = d.Discussion_Name,
                                Discussion_Description = d.Discription,
                                Comment_ID = dc.Comment_ID,
                                Comment_Description = dc.Comment_Discription,
                                Comment_CreateDate = dc.CreatedDate,
                                Comment_CreateBy = user_comments.UserName

                              });



    return View(discussion_preview);
}

模型类

public class DiscussionPreview_Model
{
    public int Disussion_ID { get; set; }
    public Nullable<System.DateTime> Discussion_CreateDate { get; set; }
    public string Discussion_CreateBy { get; set; }
    public string Discussion_Title { get; set; }
    public string Discussion_Description { get; set; }

    public int Comment_ID { get; set; }
    public Nullable<System.DateTime> Comment_CreateDate { get; set; }
    public string Comment_CreateBy { get; set; }
    public string Comment_Description { get; set; }

}

查看页面

@model IEnumerable<prjct.Models.DiscussionPreview_Model>

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

 <h3>@Html.DisplayFor(model => model.Discussion_Title)</h3>

<div>@Html.DisplayFor(model => model.Discussion_Description)</div>
<div>@Html.DisplayFor(model => model.Discussion_CreateDate)  @Html.DisplayFor(model => model.Discussion_CreateDate)</div>

@foreach (var item in Model)
{

    <fieldset>
        <legend></legend>

        <h4>Comments</h4>
        <div class="display-field">@item.Comment_Description</div>
        <div class="display-field">@item.Comment_CreateBy : @item.Comment_CreateDate </div>

    </fieldset>
}

当调试上面的应用程序时，我收到以下错误消息

'IEnumerable' does not contain a definition for 'Discussion_Title' and no extension method 'Discussion_Title' accepting a first argument of type 'IEnumerable' could be found (are you missing a using directive or an assembly reference?)

Answer 1

您的模型类型为 IEnumerable<prjct.Models.DiscussionPreview_Model>你正试图像 prjct.Models.DiscussionPreview_Model 那样使用它，这是行不通的。你将不得不循环 IEnumerable然后使用 Html.DisplayFor对于 IEnumerable 中的每个元素，就像您在评论部分所做的那样。