/// <summary>
/// DbConnectionPool 的摘要说明
/// </summary>

namespace dbopr
{
    public class DbConnectionPool
    {
        //定义存放数据库链接的队列
        private static Queue connections=new Queue();

        //数据库参数
        private static string ConnString = "";                                    //链接字符串

        //链接池参数
        private static int InitSize = 20;                                         //初始化链接池大小
        private static int MaxSize = 100;                                         //最大链接数
        private static int QueueSize = 50;                                        //队列中最大维护的链接数
        private static int ConnNum = 0;                                           //系统维护的链接总数

        //定义数据库类型，1表示为SqlServer数据库，2表示其它的OLE DB；默认为SqlServer
        private static int  DbType = 1;
        public static int DbType
        {
            set
            {
                DbType = value;
            }
        }

        private DbConnectionPool()
        {
            try{
                ConnString = Configuration.connectionStrings["DbSource"].connectionString;
                InitSize = int.Parse(Configuration.connectionStrings["InitSize"].connectionString);
                MaxSize = int.Parse(Configuration.connectionStrings["MaxSize"].connectionString);
                QueueSize = int.Parse(Configuration.connectionStrings["QueueSize"].connectionString);
                DbType = int.Parse(Configuration.connectionStrings["DbType"].connectionString);
                initPool();
            }
            catch(Exception e) {
            }
        }
       
        //初始化链接池
        private static void initPool(){
            int i;
            for (i = 1; i <= InitSize; i++) {
                if (DbType == 1)
                    connections.Enqueue(newSqlConn());
                else
                    connections.Enqueue(newOleConn());
            }
        }

        //获取一个Sql Server链接对象
        private static SqlConnection newSqlConn()
        {
            ConnNum++;
            return new SqlConnection(ConnString);
        }
       
        //获取一个OLE DB链接对像
        private static OleDbConnection newOleConn()
        {
            ConnNum++;
            return new OleDbConnection(ConnString);
        }

        //获取一个数据库链接
        public static IDbConnection getConn() {
            if (connections.Count == 0)                                  //如果队列中链接用完，则新建一个链接放入队列
            {
                if (ConnNum > MaxSize)                                   //如果当前活动链接达到最大，则等待链接
                    return null;
                else
                {
                    if (DbType == 1)
                        connections.Enqueue(newSqlConn());
                    else
                        connections.Enqueue(newOleConn());
                    return connections.Dequeue();
                }
            }
            else
                return connections.Dequeue();
        }

        //释放一个活运链接
        public static void reConn(IDbConnection conn) {
            if (connections.Count > QueueSize)                           //如果队列中元素个数已达到最大，则关闭链接
                conn.Close();
            else
                connections.Enqueue(conn);
        }

        //销毁链接池
        public static void ClearPool() {
            while(connections.Count>0)
                 (IDbConnection)connections.Dequeue().Close();
        }
    }
}

2.链接生成类
using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.OleDb;
using System.Configuration;
using System.Web;

/// <summary>
/// DbConn 的摘要说明
/// </summary>

namespace dbopr
{
    public class DbConnection
    {
        private static IDbConnection conn;
       
        public DbConnection()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        public static SqlConnection getSqlConn()
        {
            //获取链接池中的Sql Server的链接
            conn = DbConnectionPool.getConn();
            return (SqlConnection)conn;
        }

        public static OleDbConnection getOleConn() {
            //获取其它OLE DB的链接
            conn = DbConnectionPool.getConn();
            return (OleDbConnection)conn;
        }

        public static void Close() {
            //放回用过的链接
            DbConnectionPool.reConn(conn);
        }
    }
}