不包含ToPagedList的定义

Question

I keep getting this error when trying to implement PagedList in my Controller. The exact error reads

'DataIntelligence.Models.Execution' does not contain a definition for 'ToPagedList' and no extension method 'ToPagedList' accepting a first argument of type 'DataIntelligence.Models.Execution' could be found (are you missing a using directive or an assembly reference?)`

and I have no idea why. I have looked at similar question but can't seem to find the answer I am looking for. I was wondering if anybody could help.

Controller

using DataIntelligence.Models;
using PagedList;
using PagedList.Mvc;
using System;
using System.Linq;
using System.Web.Mvc;

public ActionResult Execution(int? page, int id = 0)
{
    var execution = db.Executions.Find(id);

    if (execution == null)
    {
        return HttpNotFound();
    }

    ViewBag.ExecutionSeconds = (execution.End - execution.Start).ToString(@"dd\.hh\:mm\:ss\.fff");

    int pageSize = Int32.Parse(System.Configuration.ConfigurationManager.AppSettings["DefaultPageSize"]);
                int pageNumber = (page ?? 1);
    return View(execution.ToPagedList(pageNumber, pageSize));
}

Execution Model

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;


namespace DataIntelligence.Models
{
    [Table("Execution")]
    public class Execution
    {
        public int Id { get; set; }
        public Int16 PackageId { get; set; }
        public DateTime Start { get; set; }
        public DateTime End { get; set; }
        public Boolean Successful { get; set; }

        public virtual ICollection<Step> Steps { get; set; }
    }
}

View

@model PagedList.IPagedList<DataIntelligence.Models.Execution>
@using PagedList.Mvc;

<link href="Content/PagedList.css" rel="stylesheet" type="text/css" />

@{
    ViewBag.Title = "Execution Details";
}
<script language="javascript" type="text/javascript" src="jquery-1.8.3.js">    </script>
<script>
    function goBack() {
        window.history.back();
    }
</script>
<div class="jumbotron">
    <h2>Execution Details</h2>
</div>

<fieldset>
    <legend>Execution Id - @Html.DisplayFor(model => model.Id)</legend>

    <div class="row">
        <div class="col-sm-3">
            <div class="display-label">
                @Html.DisplayNameFor(model => model.PackageId)
            </div>
            <div class="display-field">
                <a href="@Url.Action("Package", new { id=Model.PackageId})"> @Html.DisplayFor(model => model.PackageId) </a>
            </div>
        </div>

        <div class="col-sm-3">
            <div class="display-label">
                @Html.DisplayNameFor(model => model.Start)
            </div>
            <div class="display-field">
                @Html.DisplayFor(model => model.Start)
            </div>
        </div>
        <div class="col-sm-3">
            <div class="display-label">
                @Html.DisplayNameFor(model => model.End)
            </div>
            <div class="display-field">
                @Html.DisplayFor(model => model.End)
            </div>
        </div>
        <div class="col-sm-3">
            <div class="display-label">
                Execution Time
            </div>
            <div class="display-field">
                @ViewBag.ExecutionSeconds
            </div>
        </div>
    </div>
    <div class="row">
        <div class="col-sm-3">
            <div class="display-label">
                @Html.DisplayNameFor(model => model.Successful)
            </div>
            <div class="display-field">
                @Html.DisplayFor(model => model.Successful)
            </div>
        </div>
    </div>
    <br />
</fieldset>

<table>
    <tr>
        <th>
            Step ID
        </th>
        <th id="stepname">
            Name
        </th>
        <th id="stepdate">
            Date
        </th>
    </tr>

    @foreach (var step in Model.Steps) {
       <tr>
            <td>
               @Html.DisplayFor(modelItem => step.Id)
            </td>
            <td id="steps">
                @Html.DisplayFor(modelItem => step.Name)
            </td>
            <td id="date">
                @Html.DisplayFor(modelItem => step.Date)
            </td>
        </tr>
    }
</table>
<button class="btn btn-link" onclick="goBack()" style="padding-right: 0px; padding-top: 0px; padding-bottom: 0px; padding-left: 0px;">Back</button>

Page @(Model.Steps.PageCount < Model.Steps.PageNumber ? 0 :  Model.Steps.PageNumber) of @Model.Steps.PageCount
@Html.PagedListPager(Model.Steps, page => Url.Action("Execution", new { page, sortOrder = ViewBag.CurrentSort}))

Answer 1

The DbSet.Find method returns a single instance of your entity, not an enumeration. So applying ToPagedList to that does not make sense. If you did want to wrap it in a paged list, you could change your query to this:

var executions = db.Executions.Where(e => e.Id == id);

This will give you an IEnumerable result with only a single value.

Edit

After reading your comments, it seems that you actually want to paginate the Steps property only. To do that, you are better off creating a view model instead of passing the database entity directly to your view, note how I have changed the type of the Steps property to be a paged list:

public class ExecutionViewModel
{
    public int Id { get; set; }
    public Int16 PackageId { get; set; }
    public DateTime Start { get; set; }
    public DateTime End { get; set; }
    public Boolean Successful { get; set; }

    public virtual PagedList.IPagedList<Step> Steps { get; set; }
}

No your controller becomes something like this:

public ActionResult Execution(int? page, int id = 0)
{
    var execution = db.Executions.Find(id);

    if (execution == null)
    {
        return HttpNotFound();
    }

    ViewBag.ExecutionSeconds = (execution.End - execution.Start).ToString(@"dd\.hh\:mm\:ss\.fff");

    int pageSize = Int32.Parse(System.Configuration.ConfigurationManager.AppSettings["DefaultPageSize"]);
    int pageNumber = (page ?? 1);

    var executionModel = new ExecutionViewModel
    {
        Id = execution.Id,
        PackageId = execution.PackageId,
        Start = execution.Start,
        End = execution.End,
        Successful = execution.Successful,
        Steps = execution.Steps.ToPagedList(pageNumber, pageSize)
    };
    return View(executionModel);
}

And don't forget to change your view to take the new object:

@model DataIntelligence.ViewModels.ExecutionViewModel

Answer 2

Add following through NuGet:

PM> Install-Package PagedList.MVC 

In your controller, add the following:

using PagedList;

And in your view, add the following:

@using PagedList.Mvc;