程序儘可能地降低其使用的複雜性,它的優點是使用方便。現在這個程序還有一個缺點,那就是第讀取一頁的數據,都要打開一次數據庫,這個問題是可以解決的,那就是要求在不使用之用執行一個Close,關閉數據庫,這是以犧牲程序的安全性爲代價的。各個方面需要權衡利弊。
* Copryright(c) My Studio Inc. 2008-2009, all rights reserved.
* 程序名稱:數據庫分頁讀取類
* 日 期:2008年4月26日
* 作 者:汪思言
* 郵 箱:[email protected]
*
* 使用說明:
* 首先創建一個MyDataPage類實例mypage,然後設置數據庫連接串、查詢表、查詢列、查詢條件、
* 排序條件等。然後執行mypage.DoPaging(),注意檢查其返回值,返回真表示分頁成功,否則
* 應查看mypage.ErrMessage屬性。成功後,就可以使用mypage.GetData(<頁編號>)讀取數據了.
*
* 示例:
*
* using MyLibrary.DataAccess;
* MyDataPage myPage = new MyDataPage(
* "provider=sqloledb;server=(local);uid=sa;pwd=oohacker;database=Northwind",
* "Product",
* "ProductId,ProductName",
* "SupplierId<>1",
* "SupplierId ASC, ProductId DESC",
* 20);
*
* if (myPage.DoPaging())
* {
* Console.Write("Total Records: {0} Total Pages: {1} ",
* myPage.RecordCount,
* myPage.PageCount);
*
* for (int i=1; i<=myPage.PageCount; ++i)
* {
* Console.Write("Page {0} ", i);
* DataTable table = myPage.GetData(i);
* for (int j=0; j<table.Rows.Count; ++j)
* {
* Console.Write("#{0}:{1} ",
* table.Rows[j]["ProductId"],
* table.Rows[j]["ProductName"]);
* }
* }
* }
* else
* {
* Console.Write("分頁失敗!原因:{0} ", myPage.ErrMessage);
* }
*
*****************************************************************************/
using System;
using System.Text;
using System.Data;
using System.Data.OleDb;
using System.Collections;
namespace MyLibrary.DataAccess
...{
public class MyDataPage
...{
成員變量#region 成員變量
const int defaltPageSize = 10;
private int recordCount;
private int pageCount;
private int pageSize;
private string table;
private string columns;
private string conditions;
private string orders;
private string connectionString;
private string errorMessage;
private bool isDirty;
#endregion
構造函數#region 構造函數
public MyDataPage(string _connectionString, string _table)
...{
Init(_connectionString, _table, "*", "", "", defaltPageSize);
}
public MyDataPage(string _connectionString, string _table, int _pageSize)
...{
Init(_connectionString, _table, "*", "", "", _pageSize);
}
public MyDataPage(string _connectionString, string _table, string _columns, int _pageSize)
...{
Init(_connectionString, _table, _columns, "", "", _pageSize);
}
public MyDataPage(string _connectionString, string _table, string _columns, string _conditions, int _pageSize)
...{
Init(_connectionString, _table, _columns, _conditions, "", _pageSize);
}
public MyDataPage(string _connectionString, string _table, string _columns, string _conditions, string _orders, int _pageSize)
...{
Init(_connectionString, _table, _columns, _conditions, _orders, _pageSize);
}
private void Init(string _connectionString, string _table, string _columns, string _coditions, string _orders, int _pageSize)
...{
this.recordCount = -1;
this.pageCount = -1;
this.PageSize = _pageSize;
this.Table = _table;
this.Columns = _columns;
this.Conditions = _coditions;
this.Orders = _orders;
this.connectionString = _connectionString;
this.isDirty = false;
}
#endregion
// 獲取和設置頁面大小
public int PageSize
...{
set
...{
pageSize = (value >=10 && value <= 1000) ? value : defaltPageSize;
isDirty = true;
}
get
...{
return pageSize;
}
}
// 獲取記錄數
public int RecordCount
...{
get ...{ return recordCount; }
}
// 獲取頁面數
public int PageCount
...{
get ...{ return pageCount; }
}
// 獲取和設置表名
public string Table
...{
set ...{ this.table = value.Trim(); isDirty = true; }
get ...{ return this.table; }
}
// 獲取和設置要讀取的列
public string Columns
...{
set
...{
this.columns = value.Trim();
if (this.columns == "") this.columns = "*";
isDirty = true;
}
get ...{ return this.columns; }
}
// 獲取和設置讀取的條件
public string Conditions
...{
set ...{ this.conditions = value.Trim(); isDirty = true; }
get ...{ return this.conditions; }
}
// 獲取或設置排序
public string Orders
...{
set ...{ this.orders = value.Trim(); isDirty = true; }
get ...{ return this.orders; }
}
// 獲取設置連接字串
public string ConnectionString
...{
set ...{ this.connectionString = value; isDirty = true; }
get ...{ return this.connectionString; }
}
// 獲取SQL查詢命令
public string SelectCommand
...{
get
...{
StringBuilder command = new StringBuilder(256);
command.AppendFormat("select {0} from [{1}] ", columns, table);
if (conditions != "")
...{
command.AppendFormat(" where {0}", conditions);
}
if (orders != "")
...{
command.AppendFormat(" order by {0}", orders);
}
return command.ToString();
}
}
// 獲取異常信息
public string ErrMessage
...{
get ...{ return errorMessage; }
}
// 執行分頁
public bool DoPaging()
...{
errorMessage = "";
// 生成統計SQL
StringBuilder sqlParas = new StringBuilder(256);
sqlParas.AppendFormat("from [{0}] ", table);
if (conditions != "")
...{
sqlParas.AppendFormat(" where {0}", conditions);
}
String sqlCount = "select count(*) as [RowCount] " + sqlParas.ToString();
// 開始統計
OleDbConnection conn = new OleDbConnection(connectionString);
try
...{
conn.Open();
}
catch (Exception e)
...{
errorMessage = e.Message;
return false;
}
// 執行分頁獲取記錄數和頁面數信息
OleDbDataAdapter adapter = new OleDbDataAdapter();
DataSet ds = new DataSet();
try
...{
// 統計總記錄數, 得出記錄總和頁面數
adapter.SelectCommand = new OleDbCommand(sqlCount, conn);
adapter.Fill(ds, "Count");
recordCount = (int)(ds.Tables["count"].Rows[0])["RowCount"];
ds.Clear();
pageCount = recordCount / pageSize + (recordCount % pageSize > 0 ? 1 : 0);
}
catch (Exception e)
...{
errorMessage = e.Message;
return false;
}
finally
...{
conn.Close();
}
isDirty = false;
return true;
}
// 執行分頁查詢
public DataTable GetData(int page)
...{
errorMessage = "";
if (isDirty)
...{
errorMessage = "查詢條件已改變,必須先執行分頁才能再次讀取數據";
return null;
}
// 開始查詢
OleDbConnection conn = new OleDbConnection(connectionString);
try
...{
conn.Open();
}
catch (Exception e)
...{
errorMessage = e.Message;
return null;
}
// 執行分頁並讀取數據
OleDbDataAdapter adapter = new OleDbDataAdapter();
DataSet ds = new DataSet();
try
...{
// 執行分頁並讀取數據
if (page > pageCount)
...{
errorMessage = "頁面數溢出!";
return null;
}
int recordStartIndex = (page - 1) * pageSize;
adapter.SelectCommand = new OleDbCommand(this.SelectCommand, conn);
adapter.Fill(ds, recordStartIndex, pageSize, table);
}
catch (Exception e)
...{
errorMessage = e.Message;
return null;
}
finally
...{
conn.Close();
}
return ds.Tables[table];
}
}
}