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有时候桌面小程序用Access数据库是非常方便的，SQlHelper.cs如下

class SqlHelper    {        //获取数据库存放路径        private static string path = Environment.CurrentDirectory + "/DB/Pump.mdb";        private static String connStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + path + ";Jet OLEDB:Database Password=sql;";        /// 
        /// 执行增(insert)、删(delete)、改(update)的方法        /// 
        ///         ///         /// 
           public static int ExecuteNonQuery(String sql, params OleDbParameter[] parameters)        {            using (OleDbConnection conn = new OleDbConnection(connStr))            {                conn.Open();                using (OleDbCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(parameters);                    return cmd.ExecuteNonQuery();                }            }        }        /// 
        /// 一般用来执行有且只有一行一列查询结果的sql语句        /// 
        ///         ///         /// 
           public static object ExecuteScalar(String sql, params OleDbParameter[] parameters)        {            using (OleDbConnection conn = new OleDbConnection(connStr))            {                conn.Open();                using (OleDbCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(parameters);                    return cmd.ExecuteScalar();                }            }        }        /// 
        /// 用来执行多行多列的查询        /// 
        ///         ///         /// 
           public static DataTable ExecuteDataSet(String sql, params OleDbParameter[] parameters)        {            using (OleDbConnection conn = new OleDbConnection(connStr))            {                conn.Open();                using (OleDbCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(parameters);                    OleDbDataAdapter adapter = new OleDbDataAdapter(cmd);                    DataSet dataset = new DataSet();                    adapter.Fill(dataset);                    return dataset.Tables[0];                }            }        }        /// 
        /// 将null类型转换成DBNull类型        /// 
        ///         /// 
           public static Object ToDBNull(Object value)        {            if (value == null)            {                return DBNull.Value;            }            else            {                return value;            }        }        /// 
        /// 将DBNull类型转换成null类型        /// 
        ///         /// 
           public static Object ToNull(Object value)        {            if (value == DBNull.Value)            {                return null;            }            else            {                return value;            }        }        public static OleDbParameter SetParameter(String key, object value)        {            //return new OleDbParameter(key, ToDBNull(value));            if (value is DateTime?)            {                OleDbParameter time = new OleDbParameter(key, OleDbType.Date);                time.Value = ToDBNull(value);                return time;            }            else            {                return new OleDbParameter(key, ToDBNull(value));            }        }    }

#region DAL 父类提供上层操作    class BaseDAL    {        public void Delete(String tablename,  Int32? id)        {            String sql = @"delete from [" + tablename + "] where Id = @id" ;                        SqlHelper.ExecuteNonQuery(sql,SqlHelper.SetParameter("@id", id));                            }        public virtual int Save(Object entity) { return 0; }        public virtual int Update(Object entity) { return 0; }        public virtual void SetValue(DataRow row, Object o) { }            }    #endregion

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