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@SKY-HaYaTo

【C#】Web FormのLIstViewを使った高速化

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Posted at

ASP.NET Web FormによるListViewの表示処理の高速化についてです。

10万件のデータを「0.0005秒程度」で表示するのは物理的に厳しいですが（ページ読み込み＋DBアクセス＋ASP.NET処理時間を含めての意味なら現実的には 数十ms〜数百ms台が限界）、極限まで高速にページネーション表示する方法は以下の通りです。

完成イメージ

image.png

✅ パフォーマンス高速化のアプローチ（概要）

1.SQL側でページング（OFFSET FETCH）を使って最小限のデータを取得

2.SQLにインデックスを正しく設定（ORDER BY列に）

3.ListViewの仮想ページングではなく、自前でデータを制御

4.無駄な全件取得（今のような全読み込み）をしない

5.クライアント側キャッシュ（オプション）

テーブルにインデックスを設定（SQL Server）

CreateIndex.sql
CREATE NONCLUSTERED INDEX IX_employee_employeeId
ON [test].[dbo].[employee](employeeId);

image.png

修正したコード

sample4.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="sample4.aspx.cs" Inherits="WebApplicationWebForm.sample4" %>

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <meta charset="utf-8" />
    <title>ListViewページング</title>
</head>
<body>
    <form id="form2" runat="server">
        <asp:ListView ID="ListViewClass" runat="server"
            AllowPaging="false" AllowSorting="true"
            OnItemDataBound="ListViewClass_ItemDataBound"
            OnSorting="ListViewClass_Sorting">
            <LayoutTemplate>
                <table border="1" style="width:100%">
                    <thead>
                        <tr>
                            <th><asp:LinkButton ID="SortEmployeeId" runat="server" CommandName="Sort" CommandArgument="employeeId">従業員ID</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortDepartment" runat="server" CommandName="Sort" CommandArgument="department">所属部署</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSection" runat="server" CommandName="Sort" CommandArgument="section">所属課</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortJobClass" runat="server" CommandName="Sort" CommandArgument="jobclass">役職</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortName" runat="server" CommandName="Sort" CommandArgument="name">従業員名</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSex" runat="server" CommandName="Sort" CommandArgument="sex">性別</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIP" runat="server" CommandName="Sort" CommandArgument="ipaddress">IP</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIPAlloc" runat="server" CommandName="Sort" CommandArgument="ipaddressalocation">割り振り</asp:LinkButton></th>
                        </tr>
                    </thead>
                    <tbody>
                        <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
                    </tbody>
                </table>
            </LayoutTemplate>
            <ItemTemplate>
                <tr>
                    <td><%# Eval("EmployeeId") %></td>
                    <td><%# Eval("Department") %></td>
                    <td><%# Eval("Section") %></td>
                    <td><%# Eval("JobClass") %></td>
                    <td><%# Eval("Name") %></td>
                    <td><%# Eval("Sex") %></td>
                    <td><%# Eval("Ipaddress") %></td>
                    <td><%# Convert.ToBoolean(Eval("IpaddressAlocation")) ? "○" : "×" %></td>
                </tr>
            </ItemTemplate>
        </asp:ListView>

        <!-- ✅ ページングリンクをRepeaterで作成 -->
        <div style="text-align:center; margin-top:10px;">
            <asp:Repeater ID="PagerRepeater" runat="server" OnItemCommand="PagerRepeater_ItemCommand">
                <ItemTemplate>
                    <asp:LinkButton runat="server" CommandName="Page" CommandArgument='<%# Eval("PageIndex") %>'>
                        <%# Eval("DisplayText") %>
                    </asp:LinkButton>
                    &nbsp;
                </ItemTemplate>
            </asp:Repeater>
        </div>

    </form>
</body>
</html>
sample4.aspx.cs
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Configuration;
using System.Web.UI.WebControls;

namespace WebApplicationWebForm
{
    public partial class sample4 : System.Web.UI.Page
    {
        private int PageSize => 2;

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ViewState["PageIndex"] = 0;
                LoadListView();
                LoadPager();
            }
        }

        private void LoadListView()
        {
            int pageIndex = (int)ViewState["PageIndex"];
            int offset = pageIndex * PageSize;

            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            List<Sample4Employee> employees = new List<Sample4Employee>();

            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = $@"
                    SELECT employeeId, department, section, jobclass, name, sex, ipaddress, ipaddressalocation
                    FROM [test].[dbo].[employee]
                    ORDER BY {SortExpression} {SortDirection}
                    OFFSET @Offset ROWS FETCH NEXT @PageSize ROWS ONLY";

                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddWithValue("@Offset", offset);
                    cmd.Parameters.AddWithValue("@PageSize", PageSize);

                    conn.Open();
                    using (var reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            employees.Add(new Sample4Employee
                            {
                                EmployeeId = Convert.ToInt32(reader["employeeId"]),
                                Department = reader["department"].ToString(),
                                Section = reader["section"].ToString(),
                                JobClass = reader["jobclass"].ToString(),
                                Name = reader["name"].ToString(),
                                Sex = reader["sex"].ToString(),
                                Ipaddress = reader["ipaddress"].ToString(),
                                IpaddressAlocation = reader["ipaddressalocation"] != DBNull.Value &&
                                                     Convert.ToBoolean(reader["ipaddressalocation"])
                            });
                        }
                    }
                }
            }

            ListViewClass.DataSource = employees;
            ListViewClass.DataBind();
        }

        private void LoadPager()
        {
            int total = GetTotalRowCount();
            int totalPages = (int)Math.Ceiling(total / (double)PageSize);

            var pagerItems = new List<dynamic>();

            // 先頭
            pagerItems.Add(new { PageIndex = 0, DisplayText = "先頭" });

            // 番号
            for (int i = 0; i < totalPages; i++)
            {
                pagerItems.Add(new { PageIndex = i, DisplayText = (i + 1).ToString() });
            }

            // 最後尾
            pagerItems.Add(new { PageIndex = totalPages - 1, DisplayText = "最後尾" });

            PagerRepeater.DataSource = pagerItems;
            PagerRepeater.DataBind();
        }

        private int GetTotalRowCount()
        {
            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = "SELECT COUNT(*) FROM [test].[dbo].[employee]";
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    conn.Open();
                    return (int)cmd.ExecuteScalar();
                }
            }
        }

        protected void PagerRepeater_ItemCommand(object source, RepeaterCommandEventArgs e)
        {
            if (e.CommandName == "Page")
            {
                ViewState["PageIndex"] = Convert.ToInt32(e.CommandArgument);
                LoadListView();
                LoadPager();
            }
        }

        protected void ListViewClass_Sorting(object sender, ListViewSortEventArgs e)
        {
            if (SortExpression == e.SortExpression)
            {
                SortDirection = (SortDirection == "ASC") ? "DESC" : "ASC";
            }
            else
            {
                SortExpression = e.SortExpression;
                SortDirection = "ASC";
            }

            ViewState["PageIndex"] = 0;
            LoadListView();
            LoadPager();
        }

        protected void ListViewClass_ItemDataBound(object sender, ListViewItemEventArgs e)
        {
            // 任意: 装飾やロジック
        }

        private string SortExpression
        {
            get => ViewState["SortExpression"] as string ?? "employeeId";
            set => ViewState["SortExpression"] = value;
        }

        private string SortDirection
        {
            get => ViewState["SortDirection"] as string ?? "ASC";
            set => ViewState["SortDirection"] = value;
        }
    }

    public class Sample4Employee
    {
        public int EmployeeId { get; set; }
        public string Department { get; set; }
        public string Section { get; set; }
        public string JobClass { get; set; }
        public string Name { get; set; }
        public string Sex { get; set; }
        public string Ipaddress { get; set; }
        public bool IpaddressAlocation { get; set; }
    }
}

トラブルシューティング

番号リンクがリンクになっていないので、画面の切り替えができない

(修正前のコード)

sample4.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="sample4.aspx.cs" Inherits="WebApplicationWebForm.sample4" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title>ListView表示</title>
</head>
<body>
    <form id="form2" runat="server">
        <asp:ListView ID="ListViewClass" runat="server" 
            AllowPaging="false" AllowSorting="true"
            OnItemDataBound="ListViewClass_ItemDataBound"
            OnSorting="ListViewClass_Sorting"
            OnPagePropertiesChanging="ListViewClass_PagePropertiesChanging">
            <LayoutTemplate>
                <table border="1">
                    <thead>
                        <tr>
                            <th><asp:LinkButton ID="SortEmployeeId" runat="server" CommandName="Sort" CommandArgument="employeeId">従業員ID</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortDepartment" runat="server" CommandName="Sort" CommandArgument="department">所属部署</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSection" runat="server" CommandName="Sort" CommandArgument="section">所属課</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortJobClass" runat="server" CommandName="Sort" CommandArgument="jobclass">役職</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortName" runat="server" CommandName="Sort" CommandArgument="name">従業員名</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSex" runat="server" CommandName="Sort" CommandArgument="sex">性別</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIP" runat="server" CommandName="Sort" CommandArgument="ipaddress">IPアドレス</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIPAlloc" runat="server" CommandName="Sort" CommandArgument="ipaddressalocation">割り振り</asp:LinkButton></th>
                        </tr>
                    </thead>
                    <tbody>
                        <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
                    </tbody>
                </table>
            </LayoutTemplate>
            <ItemTemplate>
                <tr>
                    <td><%# Eval("EmployeeId") %></td>
                    <td><%# Eval("Department") %></td>
                    <td><%# Eval("Section") %></td>
                    <td><%# Eval("JobClass") %></td>
                    <td><%# Eval("Name") %></td>
                    <td><%# Eval("Sex") %></td>
                    <td><%# Eval("Ipaddress") %></td>
                    <td><%# Convert.ToBoolean(Eval("IpaddressAlocation")) ? "○" : "×" %></td>
                </tr>
            </ItemTemplate>
        </asp:ListView>

        <div style="margin-top:10px; text-align:center;">
            <asp:DataPager ID="DataPager1" runat="server" PagedControlID="ListViewClass" PageSize="2">
                  <Fields>
                    <asp:NextPreviousPagerField 
                        ShowFirstPageButton="true" 
                        ShowPreviousPageButton="false"
                        FirstPageText="先頭"
                        ButtonType="Link" />

                    <asp:NumericPagerField 
                        ButtonCount="10"
                        ButtonType="Link" />

                    <asp:NextPreviousPagerField 
                        ShowNextPageButton="false" 
                        ShowLastPageButton="true"
                        LastPageText="最後尾"
                        ButtonType="Link" />
                </Fields>
            </asp:DataPager>
        </div>
    </form>
</body>
</html>
sample4.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;
using WebApplicationWebForm.Models;

namespace WebApplicationWebForm
{
    public partial class sample4 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                // 最初のページ（先頭）からデータ読み込み
                DataPager1.SetPageProperties(0, DataPager1.PageSize, true);
                //DataPager1.TotalRowCount = GetTotalRowCount();
                LoadListView();
            }
        }

        private void LoadListView()
        {
            int pageSize = DataPager1.PageSize;
            int pageIndex = GetPageIndex();
            int offset = pageIndex * pageSize;

            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            List<Sample4Employee> employeeList = new List<Sample4Employee>();

            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = $@"
                    SELECT employeeId, department, section, jobclass, name, sex, ipaddress, ipaddressalocation
                    FROM [test].[dbo].[employee]
                    ORDER BY {SortExpression} {SortDirection}
                    OFFSET @Offset ROWS FETCH NEXT @PageSize ROWS ONLY";

                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddWithValue("@Offset", offset);
                    cmd.Parameters.AddWithValue("@PageSize", pageSize);

                    conn.Open();
                    SqlDataReader reader = cmd.ExecuteReader();

                    while (reader.Read())
                    {
                        employeeList.Add(new Sample4Employee
                        {
                            EmployeeId = Convert.ToInt32(reader["employeeId"]),
                            Department = reader["department"].ToString(),
                            Section = reader["section"].ToString(),
                            JobClass = reader["jobclass"].ToString(),
                            Name = reader["name"].ToString(),
                            Sex = reader["sex"].ToString(),
                            Ipaddress = reader["ipaddress"].ToString(),
                            IpaddressAlocation = reader["ipaddressalocation"] != DBNull.Value ? Convert.ToBoolean(reader["ipaddressalocation"]) : false
                        });
                    }
                }
            }

            ListViewClass.DataSource = employeeList;
            ListViewClass.DataBind();
        }

        private int GetPageIndex()
        {
            return (DataPager1.StartRowIndex / DataPager1.PageSize);
        }

        private int GetTotalRowCount()
        {
            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = "SELECT COUNT(*) FROM [test].[dbo].[employee]";
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    conn.Open();
                    return (int)cmd.ExecuteScalar();
                }
            }
        }

        protected void ListViewClass_PagePropertiesChanging(object sender, PagePropertiesChangingEventArgs e)
        {
            DataPager1.SetPageProperties(e.StartRowIndex, e.MaximumRows, false);
            LoadListView();
        }

        protected void ListViewClass_Sorting(object sender, ListViewSortEventArgs e)
        {
            if (SortExpression == e.SortExpression)
            {
                SortDirection = (SortDirection == "ASC") ? "DESC" : "ASC";
            }
            else
            {
                SortExpression = e.SortExpression;
                SortDirection = "ASC";
            }

            DataPager1.SetPageProperties(0, DataPager1.PageSize, true);
            LoadListView();
        }

        protected void ListViewClass_ItemDataBound(object sender, ListViewItemEventArgs e)
        {
            if (e.Item.ItemType == ListViewItemType.DataItem)
            {
                var employee = (Sample4Employee)((ListViewDataItem)e.Item).DataItem;
                //var employee = (Employee)((ListViewDataItem)e.Item).DataItem;
                // 色分けロジック（必要に応じて）
                // if (employee.Sex == "男") e.Item.BackColor = System.Drawing.Color.LightBlue;
                // else if (employee.Sex == "女") e.Item.BackColor = System.Drawing.Color.MistyRose;
            }
        }

        // ソート状態保持
        private string SortExpression
        {
            get => ViewState["SortExpression"] as string ?? "employeeId";
            set => ViewState["SortExpression"] = value;
        }

        private string SortDirection
        {
            get => ViewState["SortDirection"] as string ?? "ASC";
            set => ViewState["SortDirection"] = value;
        }
    }

    // モデルクラス
    public class Sample4Employee
    {
        public int EmployeeId { get; set; }
        public string Department { get; set; }
        public string Section { get; set; }
        public string JobClass { get; set; }
        public string Name { get; set; }
        public string Sex { get; set; }
        public string Ipaddress { get; set; }
        public bool IpaddressAlocation { get; set; }
    }

}

(原因)

「番号リンクが表示されるが押せない（動かない）」という原因は、AllowPaging="false" の設定と DataPager の仕様のミスマッチによるものです。

❌ 今の問題点

AllowPaging="false"：ListView 側でのページングはオフ → これは SQL側でOFFSET/FETCHを使うために必要

しかし、DataPager は AllowPaging="true" の前提で動作する部分がある（内部で ListView をトリガーにするため）

結果、ページ番号は出るがリンクとして動作しない状態になります。

✅ 解決策

👉 解決には以下のように ページングのロジックを完全にカスタムで制御する必要があります：

DataPager の代わりに 独自でページ番号リンクを出力（例：リピーターなど）

または AllowPaging="true" にしてListViewの自動ページングに任せる（ただし SQLページングでなくなり非推奨）

✅ 今回の要件（SQL OFFSET/FETCH + 高速）に合わせた対応

✅ 解決方法（推奨）

DataPager を使わず、自作のページ番号リンクを作り、ボタンクリックでページ切替する方法。

✅ 最終形コード（修正版）

sample4.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="sample4.aspx.cs" Inherits="WebApplicationWebForm.sample4" %>

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <meta charset="utf-8" />
    <title>ListViewページング</title>
</head>
<body>
    <form id="form2" runat="server">
        <asp:ListView ID="ListViewClass" runat="server"
            AllowPaging="false" AllowSorting="true"
            OnItemDataBound="ListViewClass_ItemDataBound"
            OnSorting="ListViewClass_Sorting">
            <LayoutTemplate>
                <table border="1" style="width:100%">
                    <thead>
                        <tr>
                            <th><asp:LinkButton ID="SortEmployeeId" runat="server" CommandName="Sort" CommandArgument="employeeId">従業員ID</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortDepartment" runat="server" CommandName="Sort" CommandArgument="department">所属部署</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSection" runat="server" CommandName="Sort" CommandArgument="section">所属課</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortJobClass" runat="server" CommandName="Sort" CommandArgument="jobclass">役職</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortName" runat="server" CommandName="Sort" CommandArgument="name">従業員名</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortSex" runat="server" CommandName="Sort" CommandArgument="sex">性別</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIP" runat="server" CommandName="Sort" CommandArgument="ipaddress">IP</asp:LinkButton></th>
                            <th><asp:LinkButton ID="SortIPAlloc" runat="server" CommandName="Sort" CommandArgument="ipaddressalocation">割り振り</asp:LinkButton></th>
                        </tr>
                    </thead>
                    <tbody>
                        <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
                    </tbody>
                </table>
            </LayoutTemplate>
            <ItemTemplate>
                <tr>
                    <td><%# Eval("EmployeeId") %></td>
                    <td><%# Eval("Department") %></td>
                    <td><%# Eval("Section") %></td>
                    <td><%# Eval("JobClass") %></td>
                    <td><%# Eval("Name") %></td>
                    <td><%# Eval("Sex") %></td>
                    <td><%# Eval("Ipaddress") %></td>
                    <td><%# Convert.ToBoolean(Eval("IpaddressAlocation")) ? "○" : "×" %></td>
                </tr>
            </ItemTemplate>
        </asp:ListView>

        <!-- ✅ ページングリンクをRepeaterで作成 -->
        <div style="text-align:center; margin-top:10px;">
            <asp:Repeater ID="PagerRepeater" runat="server" OnItemCommand="PagerRepeater_ItemCommand">
                <ItemTemplate>
                    <asp:LinkButton runat="server" CommandName="Page" CommandArgument='<%# Eval("PageIndex") %>'>
                        <%# Eval("DisplayText") %>
                    </asp:LinkButton>
                    &nbsp;
                </ItemTemplate>
            </asp:Repeater>
        </div>

    </form>
</body>
</html>
sample4.aspx.cs
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Configuration;
using System.Web.UI.WebControls;

namespace WebApplicationWebForm
{
    public partial class sample4 : System.Web.UI.Page
    {
        private int PageSize => 2;

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ViewState["PageIndex"] = 0;
                LoadListView();
                LoadPager();
            }
        }

        private void LoadListView()
        {
            int pageIndex = (int)ViewState["PageIndex"];
            int offset = pageIndex * PageSize;

            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            List<Sample4Employee> employees = new List<Sample4Employee>();

            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = $@"
                    SELECT employeeId, department, section, jobclass, name, sex, ipaddress, ipaddressalocation
                    FROM [test].[dbo].[employee]
                    ORDER BY {SortExpression} {SortDirection}
                    OFFSET @Offset ROWS FETCH NEXT @PageSize ROWS ONLY";

                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.Parameters.AddWithValue("@Offset", offset);
                    cmd.Parameters.AddWithValue("@PageSize", PageSize);

                    conn.Open();
                    using (var reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            employees.Add(new Sample4Employee
                            {
                                EmployeeId = Convert.ToInt32(reader["employeeId"]),
                                Department = reader["department"].ToString(),
                                Section = reader["section"].ToString(),
                                JobClass = reader["jobclass"].ToString(),
                                Name = reader["name"].ToString(),
                                Sex = reader["sex"].ToString(),
                                Ipaddress = reader["ipaddress"].ToString(),
                                IpaddressAlocation = reader["ipaddressalocation"] != DBNull.Value &&
                                                     Convert.ToBoolean(reader["ipaddressalocation"])
                            });
                        }
                    }
                }
            }

            ListViewClass.DataSource = employees;
            ListViewClass.DataBind();
        }

        private void LoadPager()
        {
            int total = GetTotalRowCount();
            int totalPages = (int)Math.Ceiling(total / (double)PageSize);

            var pagerItems = new List<dynamic>();

            // 先頭
            pagerItems.Add(new { PageIndex = 0, DisplayText = "先頭" });

            // 番号
            for (int i = 0; i < totalPages; i++)
            {
                pagerItems.Add(new { PageIndex = i, DisplayText = (i + 1).ToString() });
            }

            // 最後尾
            pagerItems.Add(new { PageIndex = totalPages - 1, DisplayText = "最後尾" });

            PagerRepeater.DataSource = pagerItems;
            PagerRepeater.DataBind();
        }

        private int GetTotalRowCount()
        {
            string connStr = ConfigurationManager.ConnectionStrings["sqlserver"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                string sql = "SELECT COUNT(*) FROM [test].[dbo].[employee]";
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    conn.Open();
                    return (int)cmd.ExecuteScalar();
                }
            }
        }

        protected void PagerRepeater_ItemCommand(object source, RepeaterCommandEventArgs e)
        {
            if (e.CommandName == "Page")
            {
                ViewState["PageIndex"] = Convert.ToInt32(e.CommandArgument);
                LoadListView();
                LoadPager();
            }
        }

        protected void ListViewClass_Sorting(object sender, ListViewSortEventArgs e)
        {
            if (SortExpression == e.SortExpression)
            {
                SortDirection = (SortDirection == "ASC") ? "DESC" : "ASC";
            }
            else
            {
                SortExpression = e.SortExpression;
                SortDirection = "ASC";
            }

            ViewState["PageIndex"] = 0;
            LoadListView();
            LoadPager();
        }

        protected void ListViewClass_ItemDataBound(object sender, ListViewItemEventArgs e)
        {
            // 任意: 装飾やロジック
        }

        private string SortExpression
        {
            get => ViewState["SortExpression"] as string ?? "employeeId";
            set => ViewState["SortExpression"] = value;
        }

        private string SortDirection
        {
            get => ViewState["SortDirection"] as string ?? "ASC";
            set => ViewState["SortDirection"] = value;
        }
    }

    public class Sample4Employee
    {
        public int EmployeeId { get; set; }
        public string Department { get; set; }
        public string Section { get; set; }
        public string JobClass { get; set; }
        public string Name { get; set; }
        public string Sex { get; set; }
        public string Ipaddress { get; set; }
        public bool IpaddressAlocation { get; set; }
    }
}
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