c#下各种数据库操作的封装！(支持ACCESS,SQLSERVER,DB2,ORACLE,MYSQL)（二）

使用静态工厂模式，通过传入枚举型参数 ，动态创建访问实例

实现模式上采用基本实现接口，派生类继承基类的虚函数，从而实现代码的耦合较低，有很好的扩展性。

public enum DBType
    ...{
        Access,
        SQL,
        DB2,
        Oracle,
        MySQL
    }

 public static class DBAccessFactory
    ...{
        public static IDBAccess Create(DBType type)
        ...{
            IDBAccess IRet = null;
            switch (type)
            ...{
                case DBType.Access:
                    IRet = new Access(type);
                    break;

                case DBType.SQL:
                    IRet = new SQL(type);
                    break;

                default:
                    break;
            }
            return IRet;
        }

        private abstract class DBAccess : IDBAccess
        ...{
            protected DbConnection m_oConn = null;
            protected const string CON_strServer = "Server";
            protected const string CON_strDataBase = "Data Source";
            protected const string CON_strUser = "UID";
            protected const string CON_strPwd = "PWD";
            protected const string CON_strConnTimeOut = "Connect Timeout = 2";
            private DBType m_eDBType = DBType.Access;

            protected DBAccess(DBType type)
            ...{
                this.m_eDBType = type;
            }

            public DBType DBType
            ...{
                get ...{ return this.m_eDBType; }
            }

            public void Init(string strServer, string strDataBase, string strUser, string strPwd)
            ...{
                this.InitConn(strServer, strDataBase, strUser, strPwd);
            }

            public void Open()
            ...{
                if (this.m_oConn != null)
                ...{
                    this.m_oConn.Open();
                }
            }

            public int RunNoQuery(string strCmd)
            ...{
                int iRet = 0;
                try
                ...{
                    DbCommand oCmd = this.GetCmd(strCmd);
                    if (oCmd != null)
                    ...{
                        iRet = oCmd.ExecuteNonQuery();
                    }
                }
                catch (Exception ex)
                ...{
                    throw (new Exception(ex.Message));
                }
                return iRet;
            }

            public int GetFiledMax(string strTable, string strField)
            ...{
                int iRet = -1;
                DataTable dt = this.RunQuery("Select Max(" + strField + ") From " + strTable);
                if (dt != null && dt.Rows.Count == 1)
                ...{
                    iRet = dt.Rows[0][0] is DBNull ? 0 : Convert.ToInt32(dt.Rows[0][0]);
                }
                return iRet;
            }

            public DataTable RunQuery(string strCmd)
            ...{
                DataTable dt = new DataTable();
                DbDataAdapter adp = this.DbAdp;
                adp.SelectCommand = this.GetCmd(strCmd);
                adp.Fill(dt);
                return dt;
            }

            public void Close()
            ...{
                if (this.m_oConn != null && this.m_oConn.State == System.Data.ConnectionState.Open)
                ...{
                    this.m_oConn.Close();
                }
            }

            public bool TestConn()
            ...{
                bool bRet = true;
                try
                ...{
                    if (this.m_oConn.State != System.Data.ConnectionState.Open)
                    ...{
                        this.m_oConn.Open();
                    }
                    bRet = this.m_oConn.State == System.Data.ConnectionState.Open;
                }
                catch
                ...{
                    bRet = false;
                }
                this.Close();
                return bRet;
            }

            public abstract DataTable Tables ...{ get; }
            public abstract DataTable GetColumns();
            public abstract DataTable GetColumns(string strTable);

            protected abstract void InitConn(string strServer, string strDataBase, string strUser, string strPwd);
            protected abstract DbCommand GetCmd(string strCmd);
            protected abstract DbDataAdapter DbAdp ...{ get;}
        }
   }