在ASP.NET網站開發中可能會遇到要更換數據庫，如將Aceess換為SQL Server?，由于Aceess引用System.Data.OleDb命名空間，SQL Server引用System.Data.SqlClient命名空間。在一般程序代碼中我們需要更改連接字符串，ADO.NET數據訪問命令對象，最麻煩的是不同數據庫有各自不同Sql命令。我們可以使用抽象工廠模式實現ASP.NET訪問不同數據庫。

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1、抽象工廠模式（Abstract Factory）：提供一個創建一系列相互依賴對象的接 口，而無需指定他們的具體類。

2、一般組成：抽象 產品接口，具體產品類，抽象工廠接口，具體工廠類，客戶端代碼

3、作用：易于交換 產品系列，在一個應用中只需在初始化的時候出現一次，這就使得改變一個應用的具體工廠的具體工廠變得非常容易，只需改變具體工廠即可使用不同的產品配置

讓具體的創建實例過程與客戶端分離，客戶端是通過他們的抽象 類接口操縱實例，產品的具體類名也被具體工廠是實現分離，不會出現在客戶代碼中。

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網上提供的代碼基本是為了講解說 明C#設計模式，由C#控制臺程序代碼實現，并沒有真正實現訪問數據庫。我這里通過建立一個ASP.NET網站，實現訪問Access與SQL Server數據庫。主要參考《大話設計模式》

具體步驟代碼如下：

1、?分別在Access和SQL Server建立數據庫DaHua與數據庫表User(ID,Name)，Department（ID,DepartName）

2、?啟動Visual Studio 2005/2008新建網站

3、?到web.config添加數據庫連接

4、?在網站解決方案右鍵新建類庫ClassLibrary1，新建類文件，包 括：

AbstractUser抽象類，SqlserverUser類，AccessUser類

AbstractDepartment抽象類，SqlserverDepartment類，AccessDepartment 類

DataAccess類

生成dll

5、到項目添加引用，項目-右鍵-添加引用-項目-ClassLibrary1

6、前臺代碼：添加一個GridView控件，三個Button控件，2個TextBox控件

用于查詢表User和Department表內容，插入User表數據

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using?System;

using?System.Configuration;

using?System.Data;

using?System.Linq;

using?System.Web;

using?System.Xml.Linq;

using?System.Data.SqlClient;

using?System.Data.OleDb;

using?System.Reflection;

?

namespace?ClassLibrary1

{

????///?<summary>

????///AbstractUser抽象類

????///?</summary>

????public?abstract?class?AbstractUser

????{

????????public?abstract?DataSet?GetUser();

????????public?abstract?void?InsertUser(string?userID,?string?userName);

????}

?

????///?<summary>

????///?SqlserverUser類

????///?</summary>

????public?class?SqlserverUser?:?AbstractUser

????{

????????string?constr?=?ConfigurationManager.ConnectionStrings["constrSQLDahua"].ConnectionString;

?

????????public?override?DataSet?GetUser()

????????{

????????????SqlConnection?conn?=?new?SqlConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

?

????????????SqlCommand?cmd?=?new?SqlCommand("select?*?from?[User]",?conn);

????????????SqlDataAdapter?sda?=?new?SqlDataAdapter();

????????????sda.SelectCommand?=?cmd;

????????????DataSet?ds?=?new?DataSet();

????????????sda.Fill(ds);

????????????return?ds;

????????}

?

????????public?override?void?InsertUser(string?userID,?string?userName)

????????{

????????????SqlConnection?conn?=?new?SqlConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

????????????SqlCommand?cmd?=?new?SqlCommand();

????????????cmd.Connection?=?conn;

????????????cmd.CommandText?=?"insert?into?[User]?values('"?+?Int32.Parse(userID)?+?"','"?+?userName?+?"')?";

????????????cmd.ExecuteNonQuery();

????????????conn.Close();

?

????????}

????}

?

????///?<summary>

????///?AccessUser類

????///?</summary>

????public?class?AccessUser?:?AbstractUser

????{

????????string?constr?=?ConfigurationManager.ConnectionStrings["constrAccessDaHua"].ConnectionString;

?

????????public?override?DataSet?GetUser()

????????{

????????????OleDbConnection?conn?=?new?OleDbConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

?

????????????OleDbCommand?cmd?=?new?OleDbCommand("select?*?from?[User]",?conn);

????????????OleDbDataAdapter?sda?=?new?OleDbDataAdapter();

????????????sda.SelectCommand?=?cmd;

????????????DataSet?ds?=?new?DataSet();

????????????sda.Fill(ds);

????????????return?ds;

????????}

?

????????public?override?void?InsertUser(string?userID,?string?userName)

????????{

????????????OleDbConnection?conn?=?new?OleDbConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

????????????OleDbCommand?cmd?=?new?OleDbCommand();

????????????cmd.Connection?=?conn;

????????????cmd.CommandText?=?"insert?into?[User]?values('"?+?Int32.Parse(userID)?+?"','"?+?userName?+?"')?";

????????????cmd.ExecuteNonQuery();

????????????conn.Close();

????????}

}

?

///?<summary>

????///AbstractDepartment抽象類

????///?</summary>

????public?abstract?class?AbstractDepartment

????{

????????public?abstract?DataSet?GetDepartment();

????????//?void?InsertDepartment(string?depID,?string?depName);

????}

?

????///?<summary>

????///?SqlserverDepartment類

????///?</summary>

????public?class?SqlserverDepartment?:?AbstractDepartment

????{

????????string?constr?=?ConfigurationManager.ConnectionStrings["constrSQLDahua"].ConnectionString;

?

????????public?override?DataSet?GetDepartment()

????????{

????????????SqlConnection?conn?=?new?SqlConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

?

????????????SqlCommand?cmd?=?new?SqlCommand("select?*?from?[Department]",?conn);

????????????SqlDataAdapter?sda?=?new?SqlDataAdapter();

????????????sda.SelectCommand?=?cmd;

????????????DataSet?ds?=?new?DataSet();

????????????sda.Fill(ds);

????????????return?ds;

?

????????}

????}

?

????///?<summary>

????///?AccessDepartment?類

????///?</summary>

????public?class?AccessDepartment?:?AbstractDepartment

????{

????????string?constr?=?ConfigurationManager.ConnectionStrings["constrAccessDaHua"].ConnectionString;

?

????????public?override?DataSet?GetDepartment()

????????{

????????????OleDbConnection?conn?=?new?OleDbConnection(constr);

????????????if?(conn.State?==?ConnectionState.Closed)

????????????????conn.Open();

?

????????????OleDbCommand?cmd?=?new?OleDbCommand("select?*?from?[Department]",?conn);

????????????OleDbDataAdapter?sda?=?new?OleDbDataAdapter();

????????????sda.SelectCommand?=?cmd;

????????????DataSet?ds?=?new?DataSet();

????????????sda.Fill(ds);

????????????return?ds;

????????}

?}

?

///?<summary>

????///DataAccess類

????///使用反射

????///?</summary>

????public?class?DataAccess

????{

????????private?static?readonly?string?AssemblyName?=?"ClassLibrary1";?//程序集名稱

????????private?static?readonly?string?db?=?"Sqlserver";?//數據庫類型名，要更改訪問的數據?庫，只需更改這里

?

????????public?static?AbstractUser?CreateUser()

????????{

????????????string?className?=?AssemblyName?+?"."?+?db?+?"User";?//命名空間.要實例化的類名

????????????return?(AbstractUser)Assembly.Load(AssemblyName).CreateInstance(className);

????????}

?

????????public?static?AbstractDepartment?CreateDepartment()

????????{

????????????string?className?=?AssemblyName?+?"."?+?db?+?"Department";

????????????return?(AbstractDepartment)Assembly.Load(AssemblyName).CreateInstance(className);

????????}

?}

}

?

前臺代碼：

public?partial?class?_Default?:?System.Web.UI.Page?

{

????ClassLibrary1.AbstractUser?au?=?null;

????ClassLibrary1.AbstractDepartment?ad?=?null;

?

????protected?void?Page_Load(object?sender,?EventArgs?e)

????{

????????

???????

????}

????protected?void?Button1_Click(object?sender,?EventArgs?e)

????{

????????au?=ClassLibrary1.DataAccess.CreateUser();

????????DataSet?ds?=?au.GetUser();

????????GridView1.DataSource?=?ds;

????????GridView1.DataBind();

?

????}

????protected?void?Button2_Click(object?sender,?EventArgs?e)

????{????????

????????string?userID?=?txtID.Text;

????????string?userName?=?txtName.Text?;

????????au?=?ClassLibrary1.DataAccess.CreateUser();

????????au.InsertUser(userID,userName);

????}

?

????//部門查詢

????protected?void?Button3_Click(object?sender,?EventArgs?e)

????{

????????ad?=?ClassLibrary1.DataAccess.CreateDepartment();

????????DataSet?ds?=?ad.GetDepartment();

????????GridView1.DataSource?=?ds;

????????GridView1.DataBind();

????}

}

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轉自：http://blog.csdn.net/canhui87/archive/2009/10/20/4704781.aspx

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