sqlpager改进版，分页的最佳选择，完整源码＋中文注释

using System;
using System.IO;
using System.Drawing;
using System.Data;
using System.Data.SqlClient;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Configuration;

namespace DevCenter
...{
    枚举 缓存模式#region 枚举 缓存模式
    public enum PagingMode
    ...{
        //缓存
        Cached,
        //不缓存
        NonCached        
    }
    #endregion
    
    枚举 导航条样式#region 枚举 导航条样式
    public enum PagerStyle
    ...{
        Character,
        NextPrev,
        NumericPages
    }
    #endregion

    枚举 排序模式#region 枚举 排序模式
    public enum SortMode
    ...{
        ASC,
        DESC
    }
    #endregion

    类 记录统计#region 类 记录统计
    public class VirtualRecordCount
    ...{
        public int RecordCount;
        public int PageCount;
        //最后一页的记录数
        public int RecordsInLastPage;
    }
    #endregion

    类 页面改变事件参数#region 类 页面改变事件参数
    public class PageChangedEventArgs : EventArgs 
    ...{
        public int OldPageIndex;
        public int NewPageIndex;
    }
    #endregion 

    SqlPager分页控件#region SqlPager分页控件

    [DefaultProperty("SelectCommand")]
    [DefaultEvent("PageIndexChanged")]
    [ToolboxData("<{0}:SqlPager runat="server" />")]
    public class SqlPager : WebControl, INamingContainer
    ...{
        私有成员#region  私有成员
            // ***********************************************************************
            // 私有成员

            //数据源
        private PagedDataSource _dataSource;
        //数据容器
        private Control _controlToPaginate;
        private string CacheKeyName 
        ...{
            get ...{return Page.Request.FilePath + "_" + UniqueID + "_Data";}
        }
        //导航条页面信息显示
        private string CurrentPageText = "当前第<font color={0}>{1}</font>页 共分<font color={0}>{2}</font>页 总计<font color={0}>{3}</font>条 每页<font color={0}>{4}</font>条";
        //导航条无记录显示
        private string NoPageSelectedText = "没有记录！";
        //格式化sql查询语句
        private string QueryPageCommandText = "SELECT * FROM " + 
            "(SELECT TOP {0} * FROM " + 
            "(SELECT TOP {1} * FROM ({2}) AS t0 ORDER BY {3} {4}) AS t1 " + 
            "ORDER BY {3} {5}) AS t2 " + 
            "ORDER BY {3} {4}";
        //格式化sql记录统计语句
        private string QueryCountCommandText = "SELECT COUNT(*) FROM ({0}) AS t0";
        // ***********************************************************************
        #endregion

        构造器#region 构造器
            // ***********************************************************************
            // 构造器
            public SqlPager() : base()
            ...{
                _dataSource = null;
                _controlToPaginate = null;

                Font.Name = "verdana";
                Font.Size = FontUnit.Point(9);
                BackColor = Color.Gainsboro; 
                ForeColor = Color.Black;
                IndexColor = Color.Black;
                BorderStyle = BorderStyle.Outset;
                BorderWidth = Unit.Parse("1px"); 
                PagingMode = PagingMode.NonCached;
                PagerStyle = PagerStyle.Character;
                CurrentPageIndex = 0;
                SelectCommand = "";
                ConnectionString = "";
                ItemsPerPage = 15;
                TotalPages = -1;
                CacheDuration = 60;
                SortMode = SortMode.DESC;
                ConnectionString = ConfigurationSettings.AppSettings["CONN_STR"];
            }
        // ***********************************************************************
        #endregion

        公共程序接口#region 公共程序接口


            方法 清空缓存#region 方法 清空缓存
                   /**//**//**//// <summary>
                   /// 方法 清空缓存
                   /// </summary>
                   public void ClearCache()
                   ...{
                       if (PagingMode == PagingMode.Cached)
                           Page.Cache.Remove(CacheKeyName); 
                   }
        #endregion

        事件 页面索引改变#region 事件 页面索引改变
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 事件 页面索引改变
            /// 当跳转到新页面时发生
            /// </summary>
            public delegate void PageChangedEventHandler(object sender, PageChangedEventArgs e);
        public event PageChangedEventHandler PageIndexChanged;
        protected virtual void OnPageIndexChanged(PageChangedEventArgs e)
        ...{
            if (PageIndexChanged != null)
                PageIndexChanged(this, e);
        }
        // ***********************************************************************
        #endregion


        属性 缓存过期时间#region 属性 缓存过期时间
            // ***********************************************************************
            // 属性 缓存过期时间
            [Description("取得或设置数据在缓存中保存多少秒")]
            public int CacheDuration
            ...{
                get ...{return Convert.ToInt32(ViewState["CacheDuration"]);}
                set ...{ViewState["CacheDuration"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 缓存模式#region 属性 缓存模式
            // ***********************************************************************
            // 属性 缓存模式
            [Description("指定数据是否需要在页面上缓存")]
            public PagingMode PagingMode
            ...{
                get ...{return (PagingMode) ViewState["PagingMode"];}
                set ...{ViewState["PagingMode"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 导航条样式#region 属性 导航条样式
            // ***********************************************************************
            // 属性 导航条样式
            [Description("指定导航条样式")]
            public PagerStyle PagerStyle
            ...{
                get ...{return (PagerStyle) ViewState["PagerStyle"];}
                set ...{ViewState["PagerStyle"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 索引值颜色#region 属性 索引值颜色
            // ***********************************************************************
            // 属性 索引值颜色
            [Description("指定索引值颜色")]
            public Color IndexColor
            ...{
                get ...{return (Color) ViewState["IndexColor"];}
                set ...{ViewState["IndexColor"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 数据容器#region 属性 数据容器
            // ***********************************************************************
            // 属性 数据容器
            [Description("取得设置数据容器的名字")]
            public string ControlToPaginate
            ...{
                get ...{return Convert.ToString(ViewState["ControlToPaginate"]);}
                set ...{ViewState["ControlToPaginate"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 每页记录数#region 属性 每页记录数
            // ***********************************************************************
            // 属性 每页记录数
            [Description("取得设置每页显示的记录数")]
            public int ItemsPerPage
            ...{
                get ...{return Convert.ToInt32(ViewState["ItemsPerPage"]);}
                set ...{ViewState["ItemsPerPage"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 当前页索引#region 属性 当前页索引
            // ***********************************************************************
            // 属性 当前页索引
            [Description("取得设置当前页面索引")]
            public int CurrentPageIndex
            ...{
                get ...{return Convert.ToInt32(ViewState["CurrentPageIndex"]);}
                set ...{ViewState["CurrentPageIndex"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 连接字符串#region 属性 连接字符串
            // ***********************************************************************
            // 属性 连接字符串
            [Description("取得设置数据库连接字符串")]
            public string ConnectionString
            ...{
                get ...{return Convert.ToString(ViewState["ConnectionString"]);}
                set ...{ViewState["ConnectionString"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 查询语句#region 属性 查询语句
            // ***********************************************************************
            // 属性 查询语句
            [Description("取得设置数据库查询语句")]
            public string SelectCommand
            ...{
                get ...{return Convert.ToString(ViewState["SelectCommand"]);}
                set ...{ViewState["SelectCommand"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 排序字段#region 属性 排序字段
            // ***********************************************************************
            // 属性 排序字段
            [Description("取得设置排序字段，仅在无缓存的模式下可用")]
            public string SortField
            ...{
                get ...{return Convert.ToString(ViewState["SortKeyField"]);}
                set ...{ViewState["SortKeyField"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 总页数#region 属性 总页数
            // ***********************************************************************
            // 属性 总页数
            // 取得显示页面的总数
            [Browsable(false)]
            public int PageCount
            ...{
                get ...{return TotalPages;}
            }
        // ***********************************************************************
        #endregion

        属性 总页数#region 属性 总页数
            // ***********************************************************************
            // 属性 总页数
            // 取得设置显示页面的总数
            protected int TotalPages
            ...{
                get ...{return Convert.ToInt32(ViewState["TotalPages"]);}
                set ...{ViewState["TotalPages"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 总记录数#region 属性 总记录数
            // ***********************************************************************
            // 属性 总记录数
            // 取得设置总记录数
            protected int TotalRecords
            ...{
                get ...{return Convert.ToInt32(ViewState["TotalRecords"]);}
                set ...{ViewState["TotalRecords"] = value;}
            }
        // ***********************************************************************
        #endregion

        属性 排序模式#region 属性 排序模式
            // ***********************************************************************
            // 属性 排序模式
            [Description("取得设置排序模式")]
            public SortMode SortMode
            ...{
                get ...{return (SortMode) ViewState["SortMode"];}
                set ...{ViewState["SortMode"] = value;}
            }
        // ***********************************************************************
        #endregion


        方法 重载 数据绑定#region 方法 重载 数据绑定
                  // ***********************************************************************
                  // 方法 重载数据绑定
                  /**//**//**//// <summary>
                  /// 取得，填充数据
                  /// </summary>
                  public override void DataBind()
                  ...{
                      // 触发数据绑定事件
                      base.DataBind();

                      // 控件必须在数据绑定后重新创建
                      ChildControlsCreated = false;

                      // 确定数据容器存在并且为列表控件(list control)
                      if (ControlToPaginate == "")
                          return;
                      _controlToPaginate = Page.FindControl(ControlToPaginate);
                      if (_controlToPaginate == null)
                          return;
                      if (!(_controlToPaginate is BaseDataList || _controlToPaginate is ListControl))
                          return;

                      // 确定数据库连接字符串有效且查询命令已指定
                      if (ConnectionString == "" || SelectCommand == "")
                          return;

                      // 取得数据
                      if (PagingMode == PagingMode.Cached)
                          FetchAllData();
                      else
                      ...{
                          //if (SortField == "")
                          //    return;
                          FetchPageData();
                      }

                      // Bind data to the buddy control
                      // 绑定数据到数据容器
                      BaseDataList baseDataListControl = null;
                      ListControl listControl = null;
                      if (_controlToPaginate is BaseDataList)
                      ...{
                          baseDataListControl = (BaseDataList) _controlToPaginate;
                          baseDataListControl.DataSource = _dataSource; 
                          baseDataListControl.DataBind();
                          return;
                      }
                      if (_controlToPaginate is ListControl)
                      ...{
                          listControl = (ListControl) _controlToPaginate;
                          listControl.Items.Clear(); 
                          listControl.DataSource = _dataSource; 
                          listControl.DataBind();
                          return;
                      }
                  }
        // ***********************************************************************
        #endregion

        方法 重载 传递数据#region 方法 重载 传递数据
                  // ***********************************************************************
                  // 方法 重载 传递数据
                  // 把数据内容传递到客户端
                  protected override void Render(HtmlTextWriter output)
                  ...{
                      // If in design-mode ensure that child controls have been created.
                      // Child controls are not created at this time in design-mode because
                      // there's no pre-render stage. Do so for composite controls like this 
                      if (Site != null && Site.DesignMode) 
                          CreateChildControls();

                      base.Render(output);
                  }
        // ***********************************************************************
        #endregion

        方法 重载 创建子控件#region 方法 重载 创建子控件
                  // ***********************************************************************
                  // 方法 重载 创建子控件
                  // Outputs the HTML markup for the control
                  protected override void CreateChildControls()
                  ...{
                      Controls.Clear();
                      ClearChildViewState();

                      BuildControlHierarchy();
                  }
        // ***********************************************************************
        #endregion


        #endregion

        私有方法#region 私有方法

            方法 创建导航条#region 方法 创建导航条
                   // ***********************************************************************
                   // 方法 创建导航条
                   private void BuildControlHierarchy()
                   ...{
                       // 导航条表格，1行2列
                       Table t = new Table();
                       t.Font.Name = Font.Name;
                       t.Font.Size = Font.Size;
                       t.BorderStyle = BorderStyle;
                       t.BorderWidth = BorderWidth;
                       t.BorderColor = BorderColor;
                       t.Width = Width;
                       t.Height = Height;
                       t.BackColor = BackColor;
                       t.ForeColor = ForeColor;

                       // 表格行
                       TableRow row = new TableRow();
                       t.Rows.Add(row);

                       // 页面索引单元格
                       TableCell cellPageDesc = new TableCell();
                       cellPageDesc.HorizontalAlign = HorizontalAlign.Right;
                       BuildCurrentPage(cellPageDesc);
                       row.Cells.Add(cellPageDesc);

                       // 导航按钮单元格
                       TableCell cellNavBar = new TableCell();

                       switch(PagerStyle)
                       ...{
                               //字符导航条
                           case PagerStyle.Character:
                               BuildCharacterUI(cellNavBar);
                               break;
                           case PagerStyle.NextPrev:
                               BuildNextPrevUI(cellNavBar);
                               break;
                           case PagerStyle.NumericPages:
                               BuildNumericPagesUI(cellNavBar);
                               break;
                           default:
                               break;
                       }

                       row.Cells.Add(cellNavBar);

                       TableCell cellTip = new TableCell();
                       cellTip.Text = "跳转到";
                       row.Cells.Add(cellTip);

                       //跳转到指定页输入框和按钮
                       TableCell cellGotoPage = new TableCell();
                       BuildGotoPage(cellGotoPage);
                       row.Cells.Add(cellGotoPage);

                       // 把表格加入到控件树
                       Controls.Add(t);
                   }
        // ***********************************************************************
        #endregion

        建立字符导航栏#region 建立字符导航栏
            /**//**//**//// <summary>
            /// 建立字符导航栏
            /// </summary>
            /// <param name="cell"></param>
            private void BuildCharacterUI(TableCell cell)
            ...{
                bool isValidPage = (CurrentPageIndex >=0 && CurrentPageIndex <= TotalPages-1);
                bool canMoveBack = (CurrentPageIndex>0);
                bool canMoveForward = (CurrentPageIndex<TotalPages-1);

                //定义首页按钮式样
                LinkButton first = new LinkButton();
                first.ID = "First";
                first.CausesValidation = false;
                first.Click += new EventHandler(first_Click);
                first.ToolTip = "首页";
                first.Text = "首页";
                first.Enabled = isValidPage && canMoveBack;
                cell.Controls.Add(first);

                //加空格
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                //定义前页按钮式样
                LinkButton prev = new LinkButton();
                prev.ID = "Prev";
                prev.CausesValidation = false;
                prev.Click += new EventHandler(prev_Click);
                prev.ToolTip = "前页";
                prev.Text = "前页";    
                prev.Enabled = isValidPage && canMoveBack;
                cell.Controls.Add(prev);

                //加空格
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                //定义后页按钮式样
                LinkButton next = new LinkButton();
                next.ID = "Next";
                next.CausesValidation = false;
                next.Click += new EventHandler(next_Click);
                next.ToolTip = "后页";
                next.Text = "后页";    
                next.Enabled = isValidPage && canMoveForward;
                cell.Controls.Add(next);

                //加空格
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                //定义尾页按钮式样
                LinkButton last = new LinkButton();
                last.ID = "Last";
                last.CausesValidation = false;
                last.Click += new EventHandler(last_Click);
                last.ToolTip = "尾页";
                last.Text = "尾页";
                last.Enabled = isValidPage && canMoveForward;
                cell.Controls.Add(last);


            }
        // ***********************************************************************
        #endregion

        BuildNextPrevUI#region BuildNextPrevUI
            // ***********************************************************************
            // PRIVATE BuildNextPrevUI
            // Generates the HTML markup for the Next/Prev navigation bar
            private void BuildNextPrevUI(TableCell cell)
            ...{
                bool isValidPage = (CurrentPageIndex >=0 && CurrentPageIndex <= TotalPages-1);
                bool canMoveBack = (CurrentPageIndex>0);
                bool canMoveForward = (CurrentPageIndex<TotalPages-1);

                // Render the << button
                LinkButton first = new LinkButton();
                first.ID = "First";
                first.Click += new EventHandler(first_Click);
                first.Font.Name = "webdings";
                first.Font.Size = FontUnit.Medium;
                first.ForeColor = ForeColor;
                first.ToolTip = "First page";
                first.Text = "7";    
                first.Enabled = isValidPage && canMoveBack;
                cell.Controls.Add(first);

                // Add a separator
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                // Render the < button
                LinkButton prev = new LinkButton();
                prev.ID = "Prev";
                prev.Click += new EventHandler(prev_Click);
                prev.Font.Name = "webdings";
                prev.Font.Size = FontUnit.Medium;
                prev.ForeColor = ForeColor;
                prev.ToolTip = "Previous page";
                prev.Text = "3";    
                prev.Enabled = isValidPage && canMoveBack;
                cell.Controls.Add(prev);

                // Add a separator
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                // Render the > button
                LinkButton next = new LinkButton();
                next.ID = "Next";
                next.Click += new EventHandler(next_Click);
                next.Font.Name = "webdings";
                next.Font.Size = FontUnit.Medium;
                next.ForeColor = ForeColor;
                next.ToolTip = "Next page";
                next.Text = "4";    
                next.Enabled = isValidPage && canMoveForward;
                cell.Controls.Add(next);

                // Add a separator
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                // Render the >> button
                LinkButton last = new LinkButton();
                last.ID = "Last";
                last.Click += new EventHandler(last_Click);
                last.Font.Name = "webdings";
                last.Font.Size = FontUnit.Medium;
                last.ForeColor = ForeColor;
                last.ToolTip = "Last page";
                last.Text = "8";
                last.Enabled = isValidPage && canMoveForward;
                cell.Controls.Add(last);
            }
        // ***********************************************************************
        #endregion

        BuildNumericPagesUI#region BuildNumericPagesUI
            // ***********************************************************************
            // PRIVATE BuildNumericPagesUI
            // Generates the HTML markup for the Numeric Pages button bar
            private void BuildNumericPagesUI(TableCell cell)
            ...{
                // Render a drop-down list  
                DropDownList pageList = new DropDownList();
                pageList.ID = "PageList";
                pageList.AutoPostBack = true;
                pageList.SelectedIndexChanged += new EventHandler(PageList_Click);
                pageList.Font.Name = Font.Name;
                pageList.Font.Size = Font.Size;
                pageList.ForeColor = ForeColor;

                // Embellish the list when there are no pages to list 
                if (TotalPages <=0 || CurrentPageIndex == -1)
                ...{
                    pageList.Items.Add("No pages");
                    pageList.Enabled = false;
                    pageList.SelectedIndex = 0; 
                }
                else // Populate the list
                ...{
                    for(int i=1; i<=TotalPages; i++)
                    ...{
                        ListItem item = new ListItem(i.ToString(), (i-1).ToString());
                        pageList.Items.Add(item);
                    }
                    pageList.SelectedIndex = CurrentPageIndex;
                }
                cell.Controls.Add(pageList);
            }
        // ***********************************************************************
        #endregion

        方法 建立跳转到指定页面#region 方法 建立跳转到指定页面
            // ***********************************************************************
            // 方法 建立跳转到指定页面
            private void BuildGotoPage(TableCell cell)
            ...{
                //                bool isValidPage = (CurrentPageIndex >=0 && CurrentPageIndex <= TotalPages-1);

                //跳转到页面索引输入框
                TextBox txbPage = new TextBox();
                txbPage.ID = "txbPage";
                txbPage.Width = 50;
                txbPage.MaxLength = 5;
                cell.Controls.Add(txbPage);

                //加空格
                cell.Controls.Add(new LiteralControl("&nbsp;"));

                //跳转到按钮
                Button btnGo = new Button();
                btnGo.ID = "btnGo";
                btnGo.Text = "确定";
                btnGo.BorderStyle = BorderStyle.Ridge;
                btnGo.BorderWidth = 1;
                btnGo.CausesValidation = false;
                btnGo.Click += new EventHandler(btnGo_Click);
                //                btnGo.Enabled = isValidPage;
                cell.Controls.Add(btnGo);

            }
        // ***********************************************************************
        #endregion

        方法 当前页索引#region 方法 当前页索引
            // ***********************************************************************
            // 方法 当前页索引
            // 从0开始
            private void BuildCurrentPage(TableCell cell)
            ...{
                Label lblIndex = new Label();
                string temp = "";

                // Use a standard template: Page X of Y
                if (CurrentPageIndex <0 || CurrentPageIndex >= TotalPages)
                ...{
                    temp = NoPageSelectedText;
                }
                else
                ...{
                    temp = String.Format(CurrentPageText, IndexColor.Name, (CurrentPageIndex+1), TotalPages, TotalRecords, ItemsPerPage);
                }

                lblIndex.Text = temp;
                cell.Controls.Add(lblIndex);

            }
        // ***********************************************************************
        #endregion

        方法 验证当前页面索引是否有效#region 方法 验证当前页面索引是否有效
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 验证索引是否有效
            /// 确定当前页面索引范围:[0,TotalPages) or -1
            /// </summary>
            private void ValidatePageIndex()
            ...{
                //如果当前页记录删除，跳到前一页
                if(CurrentPageIndex == TotalPages)
                ...{
                    CurrentPageIndex -= 1;
                }
                if (!(CurrentPageIndex >=0 && CurrentPageIndex < TotalPages))
                    CurrentPageIndex = -1;
                return;
            }
        // ***********************************************************************
        #endregion

        方法 获取全部数据(未使用)#region 方法 获取全部数据(未使用)
            // ***********************************************************************
            // PRIVATE FetchAllData
            // Runs the query for all data to be paged and caches the resulting data
            private void FetchAllData()
            ...{
                // Looks for data in the ASP.NET Cache
                DataTable data;
                data = (DataTable) Page.Cache[CacheKeyName];
                if (data == null)
                ...{
                    // Fix SelectCommand with order-by info
                    AdjustSelectCommand(true);

                    // If data expired or has never been fetched, go to the database
                    SqlDataAdapter adapter = new SqlDataAdapter(SelectCommand, ConnectionString);
                    data = new DataTable();
                    adapter.Fill(data);
                    Page.Cache.Insert(CacheKeyName, data, null, 
                        DateTime.Now.AddSeconds(CacheDuration), 
                        System.Web.Caching.Cache.NoSlidingExpiration);
                }
            
                // Configures the paged data source component
                if (_dataSource == null)
                    _dataSource = new PagedDataSource(); 
                _dataSource.DataSource = data.DefaultView; // must be IEnumerable!
                //                _dataSource.AllowPaging = true;
                _dataSource.PageSize = ItemsPerPage;
                TotalPages = _dataSource.PageCount; 
                TotalRecords = _dataSource.Count;

                // Ensures the page index is valid 
                ValidatePageIndex();
                if (CurrentPageIndex == -1)
                ...{
                    _dataSource = null;
                    return;
                }

                // Selects the page to view
                _dataSource.CurrentPageIndex = CurrentPageIndex;
            }
        // ***********************************************************************
        #endregion

        方法 获取当前页面数据#region 方法 获取当前页面数据
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 获取当前页面数据
            /// </summary>
            private void FetchPageData()
            ...{
                // 必须获得一个有效的页面索引
                // 还需要虚拟页面记录统计来验证页面索引
                AdjustSelectCommand(false);
                VirtualRecordCount countInfo = CalculateVirtualRecordCount();
                TotalPages = countInfo.PageCount;
                TotalRecords = countInfo.RecordCount;

                // 验证页面索引值的有效性（当前页面索引必须有效或为－1）
                ValidatePageIndex();
                if (CurrentPageIndex == -1)
                ...{
                    CurrentPageIndex = 0;
                    //                    return;
                }

                // 准备，运行数据库查询
                SqlCommand cmd = PrepareCommand(countInfo);
                if (cmd == null)
                    return;
                SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                DataTable data = new DataTable();
                adapter.Fill(data);

                // 配置翻页数据源组件
                if (_dataSource == null)
                    _dataSource = new PagedDataSource();
                //如果不注释下面两行,在datagrid中会出错
                //2005/12/02 by kevin@wuxi
                //                _dataSource.AllowCustomPaging = true;
                //                _dataSource.AllowPaging = true;
                _dataSource.CurrentPageIndex = 0;
                _dataSource.PageSize = ItemsPerPage;
                _dataSource.VirtualCount = countInfo.RecordCount;
                _dataSource.DataSource = data.DefaultView;    
            }
        // ***********************************************************************
        #endregion

        方法 调整查询语句#region 方法 调整查询语句
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 调整查询语句
            /// 去除查询语句中的ORDER-BY字句，改用SortField代替排序
            /// </summary>
            /// <param name="addCustomSortInfo"></param>
            private void AdjustSelectCommand(bool addCustomSortInfo)
            ...{
                // 截去查询语句中的 ORDER BY 子句
                string temp = SelectCommand.ToLower();
                int pos = temp.IndexOf("order by"); 
                if (pos > -1)
                    SelectCommand = SelectCommand.Substring(0, pos);

                // 如果定义了SortField，则加上排序
                if (SortField != "" && addCustomSortInfo)
                    SelectCommand += " ORDER BY " + SortField;
            }
        // ***********************************************************************
        #endregion

        方法 计算记录统计#region 方法 计算记录统计
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 计算记录统计
            /// 计算指定查询的记录及页面数
            /// </summary>
            /// <returns>记录统计</returns>
            private VirtualRecordCount CalculateVirtualRecordCount()
            ...{
                VirtualRecordCount count = new VirtualRecordCount();

                // 计算记录数
                count.RecordCount = GetQueryVirtualCount();
                count.RecordsInLastPage = ItemsPerPage;

                // 计算交互记录信息
                int lastPage = count.RecordCount/ItemsPerPage;
                int remainder = count.RecordCount % ItemsPerPage;
                if (remainder >0)
                    lastPage++;
                count.PageCount = lastPage;
                
                // 计算最后一页的记录数
                if (remainder >0)
                    count.RecordsInLastPage = remainder;
                return count;
            }
        // ***********************************************************************
        #endregion

        方法 格式化查询语句#region 方法 格式化查询语句
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 格式化查询语句
            /// </summary>
            /// <param name="countInfo">记录统计</param>
            /// <returns>command对象</returns>
            private SqlCommand PrepareCommand(VirtualRecordCount countInfo)
            ...{
                // 如排序字段没有定义
                if (SortField == "")
                ...{
                    // Get metadata for all columns and choose either the primary key
                    // or the 
                    // 取得所有列的数据，并取任意一列数据为主键
                    string text = "SET FMTONLY ON;" + SelectCommand + ";SET FMTONLY OFF;";
                    SqlDataAdapter adapter = new SqlDataAdapter(text, ConnectionString);
                    DataTable t = new DataTable();
                    adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
                    adapter.Fill(t);
                    DataColumn col = null;
                    if (t.PrimaryKey.Length >0)
                        col = t.PrimaryKey[0];
                    else
                        col = t.Columns[0];
                    SortField = col.ColumnName;
                }

                // 确定要得到多少条数据
                // 最后一页的数据不会多于前页
                int recsToRetrieve = ItemsPerPage;
                if (CurrentPageIndex == countInfo.PageCount-1)
                    recsToRetrieve = countInfo.RecordsInLastPage;

                string cmdText = String.Format(QueryPageCommandText, 
                    recsToRetrieve,                        // {0} --> page size
                    ItemsPerPage*(CurrentPageIndex+1),    // {1} --> size * index
                    SelectCommand,                        // {2} --> base query
                    SortField,                            // {3} --> key field in the query
                    SortMode,                           // {4} --> 排序模式
                    AlterSortMode(SortMode));

                SqlConnection conn = new SqlConnection(ConnectionString);
                SqlCommand cmd = new SqlCommand(cmdText, conn);
                return cmd;
            }

        // ***********************************************************************
        #endregion

        方法 取得总记录条数#region 方法 取得总记录条数
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 取得总记录条数
            /// </summary>
            /// <returns>总记录条数</returns>
            private int GetQueryVirtualCount()
            ...{
                string cmdText = String.Format(QueryCountCommandText, SelectCommand);
                SqlConnection conn = new SqlConnection(ConnectionString);
                SqlCommand cmd = new SqlCommand(cmdText, conn);

                cmd.Connection.Open();
                int recCount = (int) cmd.ExecuteScalar(); 
                cmd.Connection.Close();

                return recCount;
            }
        // ***********************************************************************
        #endregion

        方法 跳转到指定页面#region 方法 跳转到指定页面
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到指定页面
            /// </summary>
            /// <param name="pageIndex">页面索引</param>
            private void GoToPage(int pageIndex)
            ...{
                // 准备事件数据
                PageChangedEventArgs e = new PageChangedEventArgs();
                e.OldPageIndex = CurrentPageIndex;
                e.NewPageIndex = pageIndex;

                // 更新当前页面索引
                CurrentPageIndex = pageIndex;

                // 触发页面改变事件
                OnPageIndexChanged(e);

                // 绑定新的数据
                DataBind();
            }
        // ***********************************************************************
        #endregion

        方法 跳转到第一页#region 方法 跳转到第一页
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到第一页
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void first_Click(object sender, EventArgs e)
            ...{
                GoToPage(0);
            }
        // ***********************************************************************
        #endregion

        方法 跳转到前一页#region 方法 跳转到前一页
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到前一页
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void prev_Click(object sender, EventArgs e)
            ...{
                GoToPage(CurrentPageIndex-1);
            }
        // ***********************************************************************
        #endregion

        方法 跳转到后一页#region 方法 跳转到后一页
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到后一页
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void next_Click(object sender, EventArgs e)
            ...{
                GoToPage(CurrentPageIndex+1);
            }
        // ***********************************************************************
        #endregion

        方法 跳转到最后一页#region 方法 跳转到最后一页
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到最后一页
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void last_Click(object sender, EventArgs e)
            ...{
                GoToPage(TotalPages-1);
            }
        // ***********************************************************************
        #endregion

        方法 页面索引选择列表点击#region 方法 页面索引选择列表点击
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 页面索引选择列表点击
            /// 通过下拉框选择页面索引
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void PageList_Click(object sender, EventArgs e)
            ...{
                DropDownList pageList = (DropDownList) sender;
                int pageIndex = Convert.ToInt32(pageList.SelectedItem.Value);
                GoToPage(pageIndex);
            }
        // ***********************************************************************
        #endregion

        方法 反转排序模式#region 方法 反转排序模式
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 反转排序模式
            /// </summary>
            /// <param name="mode">排序模式</param>
            /// <returns>相反的排序模式</returns>
            private SortMode AlterSortMode(SortMode mode)
            ...{
                if(mode == SortMode.DESC)
                ...{
                    mode = SortMode.ASC;
                }
                else
                ...{
                    mode = SortMode.DESC;
                }
                return mode;
                
            }
        // ***********************************************************************
        #endregion

        方法 跳转到指定页面按钮点击#region 方法 跳转到指定页面按钮点击
            // ***********************************************************************
            /**//**//**//// <summary>
            /// 方法 跳转到指定页面按钮点击
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void btnGo_Click(object sender, EventArgs e)
            ...{
                //                bool isValidPage = (CurrentPageIndex >=0 && CurrentPageIndex < TotalPages);

                TextBox txbpage = (TextBox)FindControl("txbPage");
                if(txbpage.Text.Length > 0)
                ...{
                    int page = Convert.ToInt32(txbpage.Text.Trim());
                
                    bool isValidPage = (page -1 >= 0 && page -1 < TotalPages);
                    if(isValidPage == true)
                    ...{
                        GoToPage(page -1);
                    }
                }
            }
        // ***********************************************************************
        #endregion


        #endregion
    }
    #endregion
}