c#下各种数据库操作的封装！(支持ACCESS,SQLSERVER,DB2,ORACLE,MYSQL)（三）

各派生类的具体实现，此时只要实现DBAccess的各个虚函数即可。         private class Access : DBAccess
        ...{
            public Access(DBType type)
                : base(type)
            ...{
            }

            protected override void InitConn(string strServer, string strDataBase, string strUser, string strPwd)
            ...{
                string strConn = "Provider = ";
                switch (strDataBase.Substring(strDataBase.LastIndexOf('.') + 1).ToLower())
                ...{
                    case "mdb":     // 2000, 2003
                        strConn += "Microsoft.Jet.OleDb.4.0;";
                        break;

                    case "accdb":   // 2007
                        strConn += "Microsoft.ACE.OLEDB.12.0;";
                        break;

                    default:
                        throw (new Exception("Unknown Access Version."));
                    //break;
                }
                strConn += CON_strDataBase + " = " + strDataBase;
                //strConn += CON_strUser + " = " + strUser;
                //strConn += CON_strPwd + " = " + strPwd;
                base.m_oConn = new OleDbConnection(strConn);
            }

            protected override DbCommand GetCmd(string strCmd)
            ...{
                return new OleDbCommand(strCmd, (OleDbConnection)base.m_oConn);
            }

            protected override DbDataAdapter DbAdp
            ...{
                get ...{ return new OleDbDataAdapter(); }
            }

            public override DataTable Tables
            ...{
                get
                ...{
                    return ((OleDbConnection)base.m_oConn).GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] ...{ null, null, null, "Table" });
                }
            }

            public override DataTable GetColumns()
            ...{
                DataTable dt = new DataTable();
                foreach (DataRow row in this.Tables.Rows)
                ...{
                    dt.Merge(this.GetColumns(row["TABLE_NAME"].ToString()));
                }
                return dt;
            }

            public override DataTable GetColumns(string strTable)
            ...{
                return ((OleDbConnection)base.m_oConn).GetOleDbSchemaTable(OleDbSchemaGuid.Columns, new object[] ...{ null, null, strTable, null });
            }
        }

        private class SQL : DBAccess
        ...{
            public SQL(DBType type)
                : base(type)
            ...{
            }

            protected override void InitConn(string strServer, string strDataBase, string strUser, string strPwd)
            ...{
                string strConn = CON_strServer + " = " + strServer + ";";
                strConn += CON_strDataBase + " = " + strDataBase + ";";
                strConn += CON_strUser + " = " + strUser + ";";
                strConn += CON_strPwd + " = " + strPwd + ";";
                strConn += CON_strConnTimeOut;
                base.m_oConn = new SqlConnection(strConn);
            }

            protected override DbCommand GetCmd(string strCmd)
            ...{
                return new SqlCommand(strCmd, (SqlConnection)base.m_oConn);
            }

            protected override DbDataAdapter DbAdp
            ...{
                get ...{ return new SqlDataAdapter(); }
            }

            public override DataTable Tables
            ...{
                get ...{ return ((SqlConnection)base.m_oConn).GetSchema("Tables", null); }
            }

            public override DataTable GetColumns()
            ...{
                return ((SqlConnection)base.m_oConn).GetSchema("Columns", null);
            }

            public override DataTable GetColumns(string strTable)
            ...{
                return ((SqlConnection)base.m_oConn).GetSchema("Columns", new string[] ...{ null, null, strTable, null });
            }
        }