【4】抽象工厂模式

　　/// <summary>
    /// 下面以绝味鸭脖连锁店为例子演示下抽象工厂模式
    /// 因为每个地方的喜欢的口味不一样，有些地方喜欢辣点的，有些地方喜欢吃不辣点
    /// 客户端调用
    /// </summary>
    class Client
    {
        static void Main(string[] args)
        {
            // 南昌工厂制作南昌的鸭脖和鸭架
            AbstractFactory nanChangFactory = new NanChangFactory();
            YaBo nanChangYabo = nanChangFactory.CreateYaBo();
            nanChangYabo.Print();
            YaJia nanChangYajia= nanChangFactory.CreateYaJia();
            nanChangYajia.Print();

            // 上海工厂制作上海的鸭脖和鸭架
            AbstractFactory shangHaiFactory = new ShangHaiFactory();
            shangHaiFactory.CreateYaBo().Print();
            shangHaiFactory.CreateYaJia().Print();

            Console.Read();
        }
    }

    /// <summary>
    /// 抽象工厂类，提供创建两个不同地方的鸭架和鸭脖的接口
    /// </summary>
    public abstract class AbstractFactory
    {
        // 抽象工厂提供创建一系列产品的接口，这里作为例子，只给出了绝味中鸭脖和鸭架的创建接口
        public abstract YaBo CreateYaBo();
        public abstract YaJia CreateYaJia();
    }

    /// <summary>
    /// 南昌绝味工厂负责制作南昌的鸭脖和鸭架
    /// </summary>
    public class NanChangFactory : AbstractFactory
    {
        // 制作南昌鸭脖
        public override YaBo CreateYaBo()
        {
            return new NanChangYaBo();
        }
        // 制作南昌鸭架
        public override YaJia CreateYaJia()
        {
            return new NanChangYaJia();
        }
    }

    /// <summary>
    /// 上海绝味工厂负责制作上海的鸭脖和鸭架
    /// </summary>
    public class ShangHaiFactory : AbstractFactory
    {
        // 制作上海鸭脖
        public override YaBo CreateYaBo()
        {
            return new ShangHaiYaBo();
        }
        // 制作上海鸭架
        public override YaJia CreateYaJia()
        {
            return new ShangHaiYaJia();
        }
    }

    /// <summary>
    /// 鸭脖抽象类，供每个地方的鸭脖类继承
    /// </summary>
    public abstract class YaBo
    {
        /// <summary>
        /// 打印方法，用于输出信息
        /// </summary>
        public abstract void Print();
    }

    /// <summary>
    /// 鸭架抽象类，供每个地方的鸭架类继承
    /// </summary>
    public abstract class YaJia
    {
        /// <summary>
        /// 打印方法，用于输出信息
        /// </summary>
        public abstract void Print();
    }

    /// <summary>
    /// 南昌的鸭脖类，因为江西人喜欢吃辣的，所以南昌的鸭脖稍微会比上海做的辣
    /// </summary>
    public class NanChangYaBo : YaBo
    {
        public override void Print()
        {
            Console.WriteLine("南昌的鸭脖");
        }
    }

    /// <summary>
    /// 上海的鸭脖没有南昌的鸭脖做的辣
    /// </summary>
    public class ShangHaiYaBo : YaBo
    {
        public override void Print()
        {
            Console.WriteLine("上海的鸭脖");
        }
    }

    /// <summary>
    /// 南昌的鸭架
    /// </summary>
    public class NanChangYaJia : YaJia
    {
        public override void Print()
        {
            Console.WriteLine("南昌的鸭架子");
        }
    }

    /// <summary>
    /// 上海的鸭架
    /// </summary>
    public class ShangHaiYaJia : YaJia
    {
        public override void Print()
        {
            Console.WriteLine("上海的鸭架子");
        }
    }

　　/// <summary>
    /// 如果绝味又想开一家湖南的分店时，因为湖南喜欢吃麻的
    /// 所以这是有需要有一家湖南的工厂专门制作
    /// </summary>
    public class HuNanFactory : AbstractFactory
    {
        // 制作湖南鸭脖
        public override YaBo CreateYaBo()
        {
            return new HuNanYaBo();
        }

        // 制作湖南鸭架
        public override YaJia CreateYaJia()
        {
            return new HuNanYajia();
        }
    }

    /// <summary>
    /// 湖南的鸭脖
    /// </summary>
    public class HuNanYaBo : YaBo
    {
        public override void Print()
        {
            Console.WriteLine("湖南的鸭脖");
        }
    }

    /// <summary>
    /// 湖南的鸭架
    /// </summary>
    public class HuNanYajia : YaJia
    {
        public override void Print()
        {
            Console.WriteLine("湖南的鸭架子");
        }
    }

/// 扮演抽象工厂的角色
/// 创建连接数据库时所需要的对象集合，
/// 这个对象集合包括有 DbConnection对象（这个是抽象产品类,如绝味例子中的YaBo类）、DbCommand类、DbDataAdapter类，针对不同的具体工厂都需要实现该抽象类中方法，
public abstract class DbProviderFactory
{
    // 提供了创建具体产品的接口方法
    protected DbProviderFactory();
    public virtual DbCommand CreateCommand();
    public virtual DbCommandBuilder CreateCommandBuilder();
    public virtual DbConnection CreateConnection();
    public virtual DbConnectionStringBuilder CreateConnectionStringBuilder();
    public virtual DbDataAdapter CreateDataAdapter();
    public virtual DbDataSourceEnumerator CreateDataSourceEnumerator();
    public virtual DbParameter CreateParameter();
    public virtual CodeAccessPermission CreatePermission(PermissionState state);
}

/// 扮演着具体工厂的角色，用来创建连接SQL Server数据所需要的对象
public sealed class SqlClientFactory : DbProviderFactory, IServiceProvider
{
    // Fields
    public static readonly SqlClientFactory Instance = new SqlClientFactory();

   // 构造函数
    private SqlClientFactory()
    {
    }
    
   // 重写抽象工厂中的方法
    public override DbCommand CreateCommand()
    {  // 创建具体产品
        return new SqlCommand();
    }

    public override DbCommandBuilder CreateCommandBuilder()
    {
        return new SqlCommandBuilder();
    }

    public override DbConnection CreateConnection()
    {
        return new SqlConnection();
    }

    public override DbConnectionStringBuilder CreateConnectionStringBuilder()
    {
        return new SqlConnectionStringBuilder();
    }

    public override DbDataAdapter CreateDataAdapter()
    {
        return new SqlDataAdapter();
    }

    public override DbDataSourceEnumerator CreateDataSourceEnumerator()
    {
        return SqlDataSourceEnumerator.Instance;
    }

    public override DbParameter CreateParameter()
    {
        return new SqlParameter();
    }

    public override CodeAccessPermission CreatePermission(PermissionState state)
    {
        return new SqlClientPermission(state);
    }
}