C # Homemade database operation class Code

The source code is as follows:

Using system;using system.data;using system.data.oledb;using system.io;using system.windows.forms;namespace Test{ Class Database {public static bool Database_exists () {if (!            File.exists (Application.startuppath + "\\DataBase.mdb")) {return false;            } else {return true;  }} public OleDbConnection get_conn () {try {string conn_string                = ""; conn_string = "Data source= ' Database.mdb ';                provider=microsoft.ace.oledb.12.0; ";                OleDbConnection db_conn = new OleDbConnection (conn_string);                Db_conn.open ();            return db_conn;                } catch (Exception e) {error.database_error_conn = E.message.tostring ();            return null; }} public OleDbDataReader Select (string select_string) {TRy {if (get_conn () = = null) {return null;                } OleDbCommand db_cmd = new OleDbCommand (select_string, Get_conn ());                OleDbDataReader db_reader = Db_cmd.executereader ();                Db_reader.read ();            return db_reader;                } catch (Exception e) {error.database_error_select = E.message.tostring ();            return null; }} public int action_the_sql (string sql_string) {try {if (Get                _conn () = = null) {return 0;                } OleDbCommand db_cmd = new OleDbCommand (sql_string, Get_conn ());                int line = Db_cmd.executenonquery ();            return line;          } catch (Exception e) {error.database_error_action_the_sql = E.message.tostring ();      return 0;                }} public DataSet GetDataSet (string sql_string, String tableName) {try {                if (get_conn () = = null) {return null;                } OleDbDataAdapter Adapter = new OleDbDataAdapter (sql_string, Get_conn ());                DataSet DS = new DataSet ();                Adapter.fill (DS, tableName);            return DS;                } catch (Exception j) {error.database_error_getdataset = J.message.tostring ();            return null; }} public string GetData (string sql_string) {try {if (Get_con                N () = = null) {return null;                } OleDbCommand db_cmd = new OleDbCommand (sql_string, Get_conn ());                String data = Convert.ToString (Db_cmd.executescalar ());    return data;        } catch (Exception e) {error.database_error_action_the_sql = E.message.tostr                ING ();            return null; }        }    }}

The source code for the wrong (error) class It refers to IS as follows:

Namespace test{    class Error    {public        static string database_error_select;        public static string Database_error_conn;        public static string Database_error_action_the_sql;        public static string Database_error_getdataset;}    }

C # Homemade database operation class Code