如何在另一个模型的页面模型中显示来自模型的串联列表？答案

【问题标题】：How do I display a concatenated list from a model in another model's page model?如何在另一个模型的页面模型中显示来自模型的串联列表？
【发布时间】：2020-01-30 00:21:49
【问题描述】：

在我的主索引页面中，我想在军官姓名列中显示军官列表。即 Tommy Bahamas、Clinton K 等......

我遇到了困难，因为在索引页面上，Officer 和 SecurityLogOfficer 表不是我的 SecurityLog 模型的一部分。

安全日志索引页面

@foreach (var item in Model.SecurityLog)
    {
    <tr>
        <td style="width:4% !important">
            @Html.DisplayFor(modelItem => item.ID)
        </td>
        <td style="width:5% !important">
            @Html.DisplayFor(modelItem => item.EventDate)
        </td>


        <td style="width:5% !important">
            @Html.DisplayFor(modelItem => item.OfficerList)
        </td>
}

我创建了一个类，OfficerList，以返回逗号分隔的军官列表，但我无法在 SecurityLog 索引页面上显示它。

public class OfficerList : SecurityLog
{
    private readonly SecurityCore.Models.SecurityCoreContext _context;

    public OfficerList(SecurityCore.Models.SecurityCoreContext context)
    {
        _context = context;
    }

    public List<string> GetOfficerList()
    {
        List<string> OfficerIDs = new List<string>();

        //use the syntax .ToList() to convert object read from db to list to avoid being re-read again
        var SecLog = _context.SecurityLog.ToList();
        var SecLogOfficer = _context.SecurityLogOfficer.ToList();
        var Officer = _context.Officer.ToList();


        int rowID;

        //string[] OfficerIDs = new string[100];
        rowID = 0;

        foreach (SecurityLog sl in SecLog)
        {
            foreach (SecurityLogOfficer slo in SecLogOfficer.Where(slo => slo.SecurityLogID == sl.ID))
            {
                if (OfficerIDs[rowID] == null)
                {
                    OfficerIDs[rowID] = slo.Officer.FullName + ", ";
                }
                else
                {
                    OfficerIDs[rowID] = OfficerIDs[rowID] + slo.Officer.FullName + ", ";
                }
            }

            rowID++;
        }

        return OfficerIDs;

    }

}

这是我想显示串联列表的地方...

这是我的数据库架构和示例结果

我们将不胜感激。谢谢！

更新

在我的 SecurityLog 模型中检索串联名称列表时遇到问题。

public class SecurityLog
{
    private readonly SecurityCore.Models.SecurityCoreContext _context;

    public SecurityLog(SecurityCore.Models.SecurityCoreContext context)
    {
        _context = context;
    }

   ......

    public List<string> OfficerList
    {            
        get
        {                                
            var officerList = new OfficerList(_context);                

            return officerList.GetOfficerList();
        }
    }


 }

修改了OfficerList类

public class OfficerList : SecurityLog
{
private readonly SecurityCore.Models.SecurityCoreContext _context;

public OfficerList(SecurityCoreContext context) : base(context)
{
    _context = context;
}

public List<string> GetOfficerList()
{
    List<string> OfficerIDs = new List<string>();

    //use the syntax .ToList() to convert object read from db to list to avoid being re-read again
    var SecLog = _context.SecurityLog.ToList();
    var SecLogOfficer = _context.SecurityLogOfficer.ToList();
    var Officer = _context.Officer.ToList();


    int rowID;

    //string[] OfficerIDs = new string[100];
    rowID = 0;

    foreach (SecurityLog sl in SecLog)
    {
        foreach (SecurityLogOfficer slo in SecLogOfficer.Where(slo => slo.SecurityLogID == sl.ID))
        {
            if (OfficerIDs[rowID] == null)
            {
                OfficerIDs[rowID] = slo.Officer.FullName + ", ";
            }
            else
            {
                OfficerIDs[rowID] = OfficerIDs[rowID] + slo.Officer.FullName + ", ";
            }
        }

        rowID++;
    }

    return OfficerIDs;

}

}

我的 SecurityLog _context 说它是空的。

SqlNullValueException：数据为空。此方法或属性不能调用 Null 值。 Microsoft.Data.SqlClient.SqlBuffer.ThrowIfNull() Microsoft.Data.SqlClient.SqlBuffer.get_DateTime() Microsoft.Data.SqlClient.SqlDataReader.GetDateTime(int i) lambda_method（闭包，QueryContext，DbDataReader，ResultContext， int[] , ResultCoordinator ) Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable+Enumerator.MoveNext() System.Collections.Generic.List..ctor（IEnumerable 集合） System.Linq.Enumerable.ToList（IEnumerable 源） OfficeList.cs 中的 SecurityCore.Models.OfficerList.GetOfficerList() + var SecLog = _context.SecurityLog.ToList(); SecurityLog.cs 中的 SecurityCore.Models.SecurityLog.get_OfficerList() + 返回officerList.GetOfficerList(); Microsoft.AspNetCore.Mvc.ViewFeatures.ExpressionMetadataProvider+c__DisplayClass0_0.g__modelAccessor|0（对象容器） Microsoft.AspNetCore.Mvc.ViewFeatures.ModelExplorer.get_Model() Microsoft.AspNetCore.Mvc.ViewFeatures.TemplateBuilder..ctor（IViewEngine viewEngine, IViewBufferScope bufferScope, ViewContext viewContext, ViewDataDictionary viewData, ModelExplorer modelExplorer, string htmlFieldName, string templateName, bool readOnly, object 附加视图数据） Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.GenerateDisplay（ModelExplorer modelExplorer，字符串 htmlFieldName，字符串 templateName，对象附加视图数据） Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.DisplayFor(Expression> 表达式，字符串模板名称，字符串 htmlFieldName，对象附加视图数据） Microsoft.AspNetCore.Mvc.Rendering.HtmlHelperDisplayExtensions.DisplayFor(IHtmlHelper htmlHelper, Expression> 表达式) SecurityCore.Pages.SecurityLogs.Pages_SecurityLogs_Index.ExecuteAsync() 在 Index.cshtml 中 + @Html.DisplayFor(modelItem => item.OfficerList) Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage 页面，ViewContext 上下文） Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync（IRazorPage 页面，ViewContext 上下文，bool invokeViewStarts) Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync（ViewContext 语境） Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync（ViewContext viewContext, 字符串 contentType, Nullable statusCode) Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync（ViewContext viewContext, 字符串 contentType, Nullable statusCode) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|29_0（ResourceInvoker 调用程序，Task lastTask，State next，范围作用域，对象状态，bool isCompleted) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow（ResultExecutedContextSealed 语境） Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext(ref State next, ref Scope scope, ref object state, ref 布尔已完成） Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters() Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|24_0(ResourceInvoker 调用者，任务 lastTask，下一个状态，作用域范围，对象状态，布尔完成了） Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow（ResourceExecutedContextSealed 语境） Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next（参考状态接下来，ref Scope 范围，ref 对象状态，ref bool isCompleted) Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|19_0(ResourceInvoker 调用者，任务 lastTask，下一个状态，作用域范围，对象状态，布尔完成了） Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|17_1(ResourceInvoker 调用者） Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0（端点端点、任务 requestTask、ILogger 记录器） Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext 语境） Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext 上下文）

更新 - 添加关系

public class SecurityCoreContext : DbContext
{
    public SecurityCoreContext (DbContextOptions<SecurityCoreContext> options)
        : base(options)
    {
    }

    public DbSet<SecurityCore.Models.SecurityLog> SecurityLog { get; set; }

    public DbSet<SecurityCore.Models.Entity> Entity { get; set; }

    public DbSet<SecurityCore.Models.Location> Location { get; set; }

    public DbSet<SecurityCore.Models.ShiftRange> ShiftRange { get; set; }

    public DbSet<SecurityCore.Models.EventType> EventType { get; set; }

    public DbSet<SecurityCore.Models.SecurityLogOfficer> SecurityLogOfficer { get; set; }

    public DbSet<SecurityCore.Models.Officer> Officer { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<SecurityLogOfficer>()
            .HasKey(t => new { t.SecurityLogID, t.OfficerID });

        modelBuilder.Entity<SecurityLogOfficer>()
            .HasOne(pt => pt.SecurityLog)
            .WithMany(p => p.SecurityLogOfficers)
            .HasForeignKey(pt => pt.SecurityLogID);

        modelBuilder.Entity<SecurityLogOfficer>()
            .HasOne(pt => pt.Officer)
            .WithMany(t => t.SecurityLogOfficers)
            .HasForeignKey(pt => pt.OfficerID);
    }

}

2020 年 1 月 23 日更新

我尝试根据以下答案更新代码，但我认为这真的很接近解决；在 OfficeList 类中，目前没有 SecLog b/c 的值，在单击搜索按钮之前，页面加载上没有数据。

 OfficerList officerList = new OfficerList();
 OfficerLists = officerList.GetOfficerList(_context);

 SecurityLog = await PaginatedList<SecurityLog>.CreateAsync(sort
    .Include(a => a.Entity)
    .Include(b => b.EventType)
    .Include(c => c.Location)
    .Include(d => d.ShiftRange)
    .Include(e => e.Officer)
    .AsNoTracking(), pageIndex ?? 1, pageSize);

进入OfficerList类时为空

var SecLog = _context.SecurityLog.ToList();

SqlNullValueException：数据为空。不能对 Null 值调用此方法或属性。 Microsoft.Data.SqlClient.SqlBuffer.ThrowIfNull() Microsoft.Data.SqlClient.SqlBuffer.get_DateTime() Microsoft.Data.SqlClient.SqlDataReader.GetDateTime(int i) lambda_method（闭包，QueryContext，DbDataReader，ResultContext， int[] , ResultCoordinator ) Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable+Enumerator.MoveNext() System.Collections.Generic.List..ctor（IEnumerable 集合） System.Linq.Enumerable.ToList（IEnumerable 源） SecurityCore.Models.OfficerList.GetOfficerList(SecurityCoreContext _context) 在OfficerList.cs + var SecLog = _context.SecurityLog.ToList(); SecurityCore.Pages.SecurityLogs.IndexModel.OnGetAsync（字符串 sortOrder，字符串 currentFilter，字符串 searchString，Nullable pageIndex、字符串 entitySelect、字符串 entityFilter、DateTime dateBegin, DateTime dateBeginSelect, DateTime dateEnd, DateTime index.cshtml.cs 中的 dateEndSelect) + 官员列表 = 官员列表.GetOfficerList(_context);

OfficerList 类中是否有办法不遍历 foreach 中的 SecurityLog 并以某种方式将 SecurityLog 的 ID 作为第二个参数传递给 OfficerList（连同 _context）？

【问题讨论】：

所以...对于一个 SecurityLogId 可以有多个 OfficerID 是否正确？
是的。没错。
那么您将拥有item.OfficerList 与 SecurityLogId 中的所有官员，然后只需迭代 item.OfficerList 集合并显示所有官员。
我仍将不得不尝试，但我意识到我在填充 SecurityLog 模型中的串联名称列表时遇到问题。我已经更新了我的代码并提供了返回的 null 错误。
你和实体有正常的关系吗？或者您可以制作一个示例并将其发布在 github 上并在此处分享链接，以便人们可以帮助您

标签： c# sql asp.net-core razor-pages

【解决方案1】：

我发现您在 OfficeList 和 SecurityLog 类中多次使用依赖注入。这应该是报错的主要原因

我建议你只需要在PageModel中使用依赖注入，将_context作为参数传递给GetOfficerList方法，我认为你不需要让OfficeList继承SecurityLog类。

返回OfficeIDs集合后，使用PageModel中的OfficerLists字段存储该集合，并将SecurityLog数据集合存储到SecurityLog字段中。

同时我在您的 GetOfficerList 方法中发现了一些错误。可以直接参考以下代码进行测试。

页面模型：

public class HomeModel : PageModel
{ 
    private readonly SecurityCoreContext _context;
    public HomeModel(SecurityCoreContext context)
    {
        _context = context;
    }

    public List<string> OfficerLists { get; set; }
    public IList<SecurityLog> SecurityLog { get; set; }

    public async Task<IActionResult> OnGetAsync()
     {
        OfficerList officerList = new OfficerList();
        OfficerLists = officerList.GetOfficerList(_context);
        SecurityLog = await _context.SecurityLog.AsNoTracking().ToListAsync();
        return Page();
    }
}

OfficerList.cs

public class OfficerList
{
    public List<string> GetOfficerList(SecurityCoreContext _context)
    {
        List<string> OfficerIDs = new List<string>();

        //use the syntax .ToList() to convert object read from db to list to avoid being re-read again
        var SecLog = _context.SecurityLog.ToList();
        var SecLogOfficer = _context.SecurityLogOfficer.ToList();
        var Officer = _context.Officer.ToList();

        int rowID;
        rowID = 0;
        foreach (SecurityLog sl in SecLog)
        {
            int count = SecLogOfficer.Where(slo => slo.SecurityLogID == sl.ID).Count();
            if (count > 0)
            {
                OfficerIDs.Add("");
            }
            foreach (SecurityLogOfficer slo in SecLogOfficer.Where(slo => slo.SecurityLogID == sl.ID))
            {
                OfficerIDs[rowID] = OfficerIDs[rowID] + slo.Officer.FirstName + ", ";
            }
            if (count > 0)
            {
                OfficerIDs[rowID] = OfficerIDs[rowID].Substring(0, OfficerIDs[rowID].Length - 2);
            }
            rowID++;
        } 
        return OfficerIDs;

    }
}

页面：

@page
@model WebApplication_core_razorpage.Pages.HomeModel
@{
    ViewData["Title"] = "Home";
    Layout = "~/Pages/Shared/_Layout.cshtml";
    var i = 0;
}

<h1>Home</h1>

<table>
    @foreach (var item in Model.SecurityLog)
    {
        <tr>
            <td style="width:4% !important">
                @Html.DisplayFor(modelItem => item.ID)
            </td>
            <td style="width:5% !important">
                @Html.DisplayFor(modelItem => item.EventDate)
            </td>

            <td style="width:5% !important">
                @Model.OfficerLists[i]
            </td>
        </tr>
        i++;
    }

</table>

这是这个演示的结果：

https://i.stack.imgur.com/sz2LA.png

【讨论】：

非常感谢您的回复。我相信这接近工作，但我遇到了一个问题。如果您不介意，可以看看我的更新，以“2020 年 1 月 23 日更新”开头吗？谢谢！
我不认为将id作为参数传给OfficeList方法是个好办法，因为需要获取每个SecurityLog对应的所有名称，传参会是不必要的操作。如果您担心数据不匹配，可以对它们进行排序以确保它们对应。或者您通过 List
我能够接受您建议的答案并对其进行定制以适合我的解决方案。但是，由于我的项目中也有分页、排序和搜索，因此排序和搜索不适用于仅官员列表。我在下面的答案中发布了我的代码。谢谢！

【解决方案2】：

我能够修改@Yongqing Yu 的建议代码以使军官列表正确显示。我决定将 id 传递给 OfficerList 类并设置排序，以便我获得每一行的正确官员列表。

我最初并没有发布这个逻辑，但我已经根据 Microsoft 的 Contoso 大学的演示实现了排序、搜索和分页。
https://docs.microsoft.com/en-us/aspnet/core/data/ef-rp/sort-filter-page?view=aspnetcore-3.1

使用新实现的代码，排序和过滤不再适用于军官列表。其他一切都按预期工作。

如何在下面的当前代码中解决排序和搜索问题？更具体地说...如何读取（迭代）OfficerID 列表并搜索每个列表项的字符串值（连接的军官列表行）？

foreach (SecurityLog secLog in SecurityLog)
        {
            secLogCopy = secLog;

            OfficerLists = officerList.GetOfficerList(_context, secLog, rowID, OfficerIDs);
            if (!String.IsNullOrEmpty(searchString))
            {
                sort = sort.Where(s => OfficerIDs.ToString().Contains(searchString));
            }
            rowID++;
        }

页面模型：

namespace SecurityCore.Pages.SecurityLogs
{
    public class IndexModel : PageModel
    {
        private readonly SecurityCore.Models.SecurityCoreContext _context;

        public IndexModel(SecurityCore.Models.SecurityCoreContext context)
        {
            _context = context;
        }

        public string EventDateSort { get; set; }
        public string EventStartSort { get; set; }
        public string EventEndSort { get; set; }
        public string ContactNameSort { get; set; }
        public string EventTypeSort { get; set; }
        public string ShiftRangeSort { get; set; }

        public string CurrentSort { get; set; }
        public string IDSort { get; set; }

        [DataType(DataType.Date)]
        public Nullable<DateTime> DateEnd { get; set; }
        [DataType(DataType.Date)]
        public Nullable<DateTime> DateBegin { get; set; }
        public Entity Entity { get; set; }


        public PaginatedList<SecurityLog> SecurityLog { get; set; }
        public List<secLog> SecurityLogOfficers { get; set; } = new List<secLog>();
        public List<string> OfficerLists { get; set; }

        [BindProperty]
        public OfficerList officerList { get; set; } = new OfficerList();
        [BindProperty]
        public List<string> OfficerIDs { get; set; } = new List<string>();







    public async Task OnGetAsync(string sortOrder, string currentFilter, string searchString, int? pageIndex,
                                 string entitySelect, string entityFilter, DateTime dateBegin, DateTime dateBeginSelect, DateTime dateEnd, DateTime dateEndSelect)
    {
        selectedEntity = new SelectList(_context.Entity.Where(a => a.Active == "Y"), "Name", "Name");

        CurrentSort = sortOrder;
        IDSort = sortOrder == "ID" ? "ID_Desc" : "ID";
        EventDateSort = sortOrder == "EventDate" ? "EventDate_Desc" : "EventDate";
        ContactNameSort = sortOrder == "ContactName" ? "ContactName_Desc" : "ContactName";
        EventTypeSort = sortOrder == "EventType" ? "EventType_Desc" : "EventType";
        ShiftRangeSort = sortOrder == "ShiftRange" ? "ShiftRange_Desc" : "ShiftRange";            
        OfficerNameSort = sortOrder == "OfficerName" ? "OfficerName_Desc" : "OfficerName";


        IQueryable<SecurityLog> sort = from s in _context.SecurityLog select s;


        switch (sortOrder)
        {
            case "ID_Desc":
                sort = sort.OrderByDescending(s => s.ID);
                break;
            case "ID":
                sort = sort.OrderBy(s => s.ID);
                break;
            case "EventDate":
                sort = sort.OrderBy(s => s.EventDate);
                break;                
            case "ShiftRange":
                sort = sort.OrderBy(s => s.ShiftRange.Name).ThenBy(s => s.EventDate);
                break;
            case "ShiftRange_Desc":
                sort = sort.OrderByDescending(s => s.ShiftRange.Name).ThenBy(s => s.EventDate);
                break;
            case "EventType":
                sort = sort.OrderBy(s => s.EventType.Name).ThenBy(s => s.EventDate);
                break;
            case "EventType_Desc":
                sort = sort.OrderByDescending(s => s.EventType.Name).ThenBy(s => s.EventDate);
                break;                
            case "OfficerName":                    
                sort = sort.OrderBy(s => officerList.ToString()).ThenBy(s => s.EventDate);
                break;
            case "OfficerName_Desc":                    
                sort = sort.OrderByDescending(s => officerList.ToString()).ThenBy(s => s.EventDate);
                break;
            default:
                sort = sort.OrderByDescending(s => s.EventDate);
                break;
        }

        int pageSize = 5;





        SecurityLog = await PaginatedList<SecurityLog>.CreateAsync(sort
        .Include(a => a.Entity)
        .Include(b => b.EventType)
        .Include(c => c.Location)
        .Include(d => d.ShiftRange)
        .Include(e => e.Officer)                                    
        .AsNoTracking(), pageIndex ?? 1, pageSize);



        int rowID;
        rowID = 0;


        foreach (SecurityLog secLog in SecurityLog)
        {
            secLogCopy = secLog;
            OfficerLists = officerList.GetOfficerList(_context, secLog, rowID, OfficerIDs);
            if (!String.IsNullOrEmpty(searchString))
            {
                sort = sort.Where(s => OfficerIDs.ToString().Contains(searchString));
            }
            rowID++;
        }



        if (!String.IsNullOrEmpty(searchString))
        {                                                

            sort = sort.Where(s => s.Narrative.Contains(searchString)
                                || s.RecordLocked.Contains(searchString)
                                || s.ContactName.Contains(searchString)
                                || s.Location.Name.Contains(searchString)
                                || s.EventType.Name.Contains(searchString)
                                || s.ShiftRange.Name.Contains(searchString)
                                || s.ID.ToString().Contains(searchString)
                                || s.SubjectFirst.Contains(searchString)
                                || s.SubjectLast.Contains(searchString));                                    
        }

    }

}

}

OfficerList.cs

public class OfficerList
{
    public List<string> GetOfficerList(SecurityCoreContext _context, SecurityLog secLog, int rowID, List<string> OfficerIDs)
    {            

        int CurrentID = secLog.ID;

        var SecLogOfficer = _context.SecurityLogOfficer.ToList();
        var Officer = _context.Officer.ToList();


        int count = SecLogOfficer.Where(slo => slo.SecurityLogID == CurrentID).Count();

        if (count >= 0)
        {
            OfficerIDs.Add("");
        }
        foreach (secLog slo in SecLogOfficer.Where(slo => slo.SecurityLogID == CurrentID))
        {
            OfficerIDs[rowID] = OfficerIDs[rowID] + slo.Officer.FullName + ", ";
        }
        if (count > 0)
        {
            OfficerIDs[rowID] = OfficerIDs[rowID].Substring(0, OfficerIDs[rowID].Length - 2);
        }


        return OfficerIDs;

    }

}

页面：

@page
@model WebApplication_core_razorpage.Pages.HomeModel
@{
    ViewData["Title"] = "Home";
    Layout = "~/Pages/Shared/_Layout.cshtml";
    var i = 0;
}

<h1>Home</h1>

<table>
    @foreach (var item in Model.SecurityLog)
    {
        <tr>
            <td style="width:4% !important">
                @Html.DisplayFor(modelItem => item.ID)
            </td>
            <td style="width:5% !important">
                @Html.DisplayFor(modelItem => item.EventDate)
            </td>

            <td style="width:5% !important">
                @Model.OfficerLists[i]
            </td>
        </tr>
        i++;
    }

</table>

分页列表.cs

public class PaginatedList<T> : List<T>
{
    public int PageIndex { get; private set; }
    public int TotalPages { get; private set; }        

    public PaginatedList(List<T> items, int count, int pageIndex, int pageSize)
    {
        PageIndex = pageIndex;
        TotalPages = (int)Math.Ceiling(count / (double)pageSize);

        this.AddRange(items);
    }

    public bool HasPreviousPage
    {
        get
        {
            return (PageIndex > 1);
        }
    }


    public bool HasNextPage => PageIndex < TotalPages;

    public bool ShowFirst
    {
        get
        {
            return (PageIndex != 1);
        }
    }

    public bool ShowLast
    {
        get
        {
            return (PageIndex != TotalPages);
        }
    }

    public static async Task<PaginatedList<T>> CreateAsync(
        IQueryable<T> source, int pageIndex, int pageSize)
    {
        var count = await source.CountAsync();
        var items = await source.Skip(
            (pageIndex - 1) * pageSize)
            .Take(pageSize).ToListAsync();
        return new PaginatedList<T>(items, count, pageIndex, pageSize);
    }
}

【讨论】：