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简单工厂模式，工厂方法模式，抽象工厂模式

以前都是以记录笔记的方式写很短的随笔；然而这一次比较长，由于时间，表达能力，理解能力有限，肯定有很多不完整和错误的地方，请各位多多包含，后期会不断完善和修改；谢谢！

面向对象方法设计就是用封装，继承，多态来实现代码的可维护，可扩展，可复用，灵活性好。

面向过程编程：

从以前面向过程编程开始，很多代码都写在一起，比如对一用户，具备获取与新增它的功能。

static void Main(string[] args) {  try  {   Console.Write("请输入数字Get or Insert：");   string strOperation=Console.ReadLine();   switch(strOperation)   {    case "Get": 
    Console.WriteLine("在SQL Server中给Department表增加一条记录");
     break;    case "Insert": 
    Console.WriteLine("在SQL Server中根据ID得到给Department表一条记录"); 
    break;   }  }  catch(Exception e)  {   Console.WriteLine("程序出现异常："+e.Message);  }  }

但以上代码修改时会牵一发而动全身，很可能牵扯到其他不应该修改的代码，如果代码长的话进行维护时甚至自己都不认识，而且代码的复用性也不高。这时面向对象编程就起到了作用。所以我们需要对代码进行封装。

面向对象编程，对界面与业务的分离

public class Department {     public static string GetResult(string strOperation)   {    string result=string.Empty;    switch(strOperation)    {      case "Insert": result = "在SQL Server中给Department表增加一条记录"; 
       break;      case "Get": result = "在SQL Server中根据ID得到给Department表一条记录"; 
     break;    }    return result;   }  }  public class Program   {     static void Main(string[] args)     {     try     {      Console.Write("请输入数字Insert or Get：");      string strOperation=Console.ReadLine();      string strResult = Department.GetResult(strOperation);      Console.WriteLine(strResult);     }     catch(Exception e)     {      Console.WriteLine("程序出现异常："+e.Message);     }     } }

但是，这时，如果我们需要对业务中新增其他功能，如删除，那就会对修改开放了，违背了“开放-封闭”原则：只能对扩张开放，而不能对修改开放。所以我们需要对操作进行分离和封装。

public class Department  {   public string strResult = string.Empty;   public virtual string GetResult()   {             return strResult;   }  }  class InsertSqlserverDepartment : Department  {    public override string GetResult()    {     strResult = "在SQL Server中给Department表增加一条记录";     return strResult;    }  }  class GetSqlserverDepartment : Department  {    public override string GetResult()    {     strResult = "在SQL Server中根据ID得到给Department表一条记录";     return strResult;    }  }  public class Program   {     static void Main(string[] args)     {      //Console.WriteLine("请输入你所要的操作，Insert or Get");      //string strOperation = Console.ReadLine();      Department oper;      oper = new GetSqlserverDepartment();      string strResult = oper.GetResult();      Console.WriteLine(strResult);      Console.ReadLine();     }   }

但是我想

1.简单工程模式

public class Department {  public string strResult = string.Empty;  public virtual string GetResult()  {            return strResult;  } } class InsertSqlserverDepartment : Department {   public override string GetResult()   {    strResult = "在SQL Server中给Department表增加一条记录";    return strResult;   } } class GetSqlserverDepartment : Department {   public override string GetResult()   {    strResult = "在SQL Server中根据ID得到给Department表一条记录";    return strResult;   } } public class DepartmentFactory {  public static Department createDepartmentOperation(string type)  {   Department dept = null;   switch (type)   {    case "Insert": dept = new InsertSqlserverDepartment(); break;    case "Get": dept = new GetSqlserverDepartment(); break;   }   return dept;  } } public class Program  {    static void Main(string[] args)    {     Console.WriteLine("请输入你所要的操作，Insert or Get");     string strOperation = Console.ReadLine();     Department oper;     oper =DepartmentFactory.createDepartmentOperation(strOperation);     string strResult = oper.GetResult();     Console.WriteLine(strResult);     Console.ReadLine();    }  }

但是，我们可能操作不同数据库的同一个产品，此时就要添加另一种数据操作类了，以下的模式就派上用场了。

2.工厂方法模式

class Department    {     public int ID{get;set;}     public int DeptName{get;set;}    }    interface IDepartment    {     void Insert(Department dept);     Department GetDepartment(int id);    }    class SqlserverDepartment : IDepartment    {     public void Insert(Department department)     {      Console.WriteLine("在SQL Server中给Department表增加一条记录");     }     public void GetDepartment(int id)     {      Console.WriteLine("在SQL Server中根据ID得到给Department表一条记录");     }    }    class OracleDepartment : IDepartment    {     public void Insert(Department department)     {      Console.WriteLine("在Oracle中给Department表增加一条记录");     }     public void GetDepartment(int id)     {      Console.WriteLine("在Oracle中根据ID得到给Department表一条记录");     }    }    interface IFactory    {     IDepartment CreateDepartment();    }    class SqlServerFactory : IFactory    {     public IDepartment CreateDepartment()     {      return new SqlserverDepartment();     }    }    class OracleFactory : IFactory    {     public IDepartment CreateDepartment()     {      return new OracleDepartment();     }    }    public class Program     {    static void Main(string[] args)    {        Department dept = new Department();     //IFactory factory = new SqlServerFactory();     IFactory factory = new OracleFactory();     IDepartment idept = factory.CreateDepartment();     idept.Insert(dept);     idept.GetDepartment(1);     Console.ReadLine();    } }

但是我们一般操作数据库，不只是操作一张表，很可能还会有用户表，那我们继续添加，这里就有了以下的设计模式

3.抽象工厂模式

  class Department {  public int ID{get;set;}  public int DeptName{get;set;} } class User {  public int ID { get; set; }  public int UserName { get; set; } } interface IDepartment {  void Insert(Department department);  Department GetDepartment(int id); } interface IUser {  void Insert(User user);  User GetUser(int id); } class SqlserverDepartment : IDepartment {  public void Insert(Department department)  {   Console.WriteLine("在SQL Server中给Department表增加一条记录");  }  public void GetDepartment(int id)  {   Console.WriteLine("在SQL Server中根据ID得到给Department表一条记录");  } } class OracleDepartment : IDepartment {  public void Insert(Department department)  {   Console.WriteLine("在Oracle中给Department表增加一条记录");  }  public void GetDepartment(int id)  {   Console.WriteLine("在Oracle中根据ID得到给Department表一条记录");  } } class SqlserverUser : IUser {  public void Insert(User user)  {   Console.WriteLine("在SQL Server中给User表增加一条记录");  }  public void GetDUser(int id)  {   Console.WriteLine("在SQL Server中根据ID得到给User表一条记录");  } } class OracleUser : IUser {  public void Insert(User user)  {   Console.WriteLine("在Oracle中给User表增加一条记录");  }  public void GetUser(int id)  {   Console.WriteLine("在Oracle中根据ID得到给User表一条记录");  } } interface IFactory {  IUser CreateUser();  IDepartment CreateDepartment(); } class SqlServerFactory : IFactory {  public IUser CreateUser()  {   return new SqlserverUser();  }  public IDepartment CreateDepartment()  {   return new SqlserverDepartment();  } } class OracleFactory : IFactory {  public IUser CreateUser()  {   return new OracleUser();  }  public IDepartment CreateDepartment()  {   return new OracleDepartment();  } } class Program {  static void Main(string[] args)  {   User user = new User();   Department dept = new Department();   //IFactory factory = new SqlServerFactory();   IFactory factory = new OracleFactory();   IUser iu = factory.CreateUser();   iu.Insert(user);   iu.GetUser(1);   IDepartment idept = factory.CreateDepartment();   idept.Insert(dept);   idept.GetDepartment(1);   Console.ReadLine();  } }