工厂方法模式切换数据库 echo

工厂方法（FactoryMethod），我也就一句话了：具体的子工厂生产具体的产品，解决了OO的“开放-封闭”原则。

  一、先看图：

  二、具体实现代码：

        1、产品类

using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Data.OleDb;

namespace FactoryLibrary
{
    /// <summary>
    /// 抽象产品基类
    /// </summary>
    public abstract class Product
    {
        abstract public DataTable GetData();
    }
    /// <summary>
    /// 具体产品SQL Server2005,继承自Product类
    /// </summary>
    public class SqlServer2005 : Product
    {
        string connectionString = string.Empty;
        SqlConnection connection = null;
        SqlCommand cmd = null;
        SqlDataAdapter dap = null;
        DataTable table = null;
        /// <summary>
        /// 读取SQL Server数据库
        /// </summary>
        /// <returns></returns>
        public override DataTable GetData()
        {
            try
            {
                connectionString = ConfigurationManager.ConnectionStrings["sqlConn"].ConnectionString.ToString();
                connection = new SqlConnection(connectionString);
                cmd = new SqlCommand("SELECT EmployeeID,LastName,FirstName,Title FROM Employees", connection);
                dap = new SqlDataAdapter(cmd);
                table = new DataTable();
                dap.Fill(table);
                return table;
            }
            catch
            {
                return null;
            }
            finally
            {
                table.Dispose();
            }
        }
    }
    /// <summary>
    /// 具体产品Access,继承自Product类
    /// </summary>
    public class Access : Product
    {
        string connectionString = string.Empty;
        OleDbConnection connection = null;
        OleDbCommand cmd = null;
        OleDbDataAdapter dap = null;
        DataTable table = null;
        /// <summary>
        /// 读取Access数据库
        /// </summary>
        /// <returns></returns>
        public override DataTable GetData()
        {
            try
            {
                connectionString = ConfigurationManager.ConnectionStrings["accessConn"].ConnectionString.ToString();
                connection = new OleDbConnection(connectionString);
                cmd = new OleDbCommand("SELECT ID,姓氏,名字,电子邮件地址 FROM 员工", connection);
                dap = new OleDbDataAdapter(cmd);
                table = new DataTable();
                dap.Fill(table);
                return table;
            }
            catch
            {
                return null;
            }
            finally
            {
                table.Dispose();
            }
        }
    }
    /// <summary>
    /// 具体产品Oracle,继承自Product类
    /// </summary>
    public class Oracle : Product
    {
        /// <summary>
        /// 读取Oracle数据库
        /// </summary>
        /// <returns></returns>
        public override DataTable GetData() { return null; }
    }
}

  2、工厂类

 

namespace FactoryLibrary
{
    /// <summary>
    /// 抽象工厂类
    /// </summary>
    public abstract class Factory
    {
        /// <summary>
        /// 工厂方法
        /// </summary>
        abstract public Product createDataBase();
    }
    /// <summary>
    /// SQL Server工厂，继承自Factory类
    /// </summary>
    public class SqlServerFactory : Factory
    {
        /// <summary>
        /// 返回SQL Server产品
        /// </summary>
        /// <returns></returns>
        public override Product createDataBase()
        {
            return new SqlServer2005();
        }
    }
    /// <summary>
    /// Access工厂，继承自Factory类
    /// </summary>
    public class AccessFactory : Factory
    {
        /// <summary>
        /// 返回Access产品
        /// </summary>
        /// <returns></returns>
        public override Product createDataBase()
        {
            return new Access();
        }
    }
    /// <summary>
    /// Oracle工厂，继承自Factory类
    /// </summary>
    public class OracleFactory : Factory
    {
        /// <summary>
        /// 返回Oracle产品
        /// </summary>
        /// <returns></returns>
        public override Product createDataBase()
        {
            return new Oracle();
        }
    }
}

  3、客户端

using System;
using System.Windows.Forms;
using FactoryLibrary;

namespace FactoryMethod
{
    public partial class mainForm : Form
    {
        public mainForm()
        {
            InitializeComponent();
            this.rbtnSQLServer.CheckedChanged += new EventHandler(rbtn_CheckedChanged);
            this.rbtnOracle.CheckedChanged += new EventHandler(rbtn_CheckedChanged);
            this.rbtnAccess.CheckedChanged += new EventHandler(rbtn_CheckedChanged);
        }
        /// <summary>
        /// 事件调用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void rbtn_CheckedChanged(object sender, EventArgs e)
        {
            selectedDB = ((RadioButton)sender).Text;
            this.lblSelectedInfo.Text = "您选择了" + selectedDB + "数据库！";
            this.gboxSelect.Enabled = false;
            this.btnShowData.Enabled = true;
        }

        /// <summary>
        /// 切换数据库
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnSelectNewDB_Click(object sender, EventArgs e)
        {
            if (this.gboxSelect.Enabled == true)
            {
                MessageBox.Show("您还没有选择数据库，请选择！", "提示！", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
            }
            this.rbtnSQLServer.Checked = false;
            this.rbtnOracle.Checked = false;
            this.rbtnAccess.Checked = false;
            this.gboxSelect.Enabled = true;
            this.lblSelectedInfo.Text = null;
            this.btnShowData.Enabled = false;
            this.dgvShowData.DataSource = null;
        }
        /// <summary>
        /// 存放客户端所选择的数据库
        /// </summary>
        private string selectedDB = null;
        /// <summary>
        /// 访问数据库显示数据
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnShowData_Click(object sender, EventArgs e)
        {
            switch (selectedDB)
            {
                case "SQL Server2005":
                    this.dgvShowData.DataSource = new SqlServerFactory().createDataBase().GetData();
                    break;
                case "Oracle":
                    break;
                case "Access":
                    this.dgvShowData.DataSource = new AccessFactory().createDataBase().GetData();
                    break;
                default:
                    break;
            }
        }
    }
}

 三、没了。