高效使用数据库的连接

    (1)     try
            {

            }
            catch (Exception)
            {

                throw;
            }
            finally 
            {
            }

     (2)     using (SqlConnection conn=new SqlConnection("数据库连接字符串"))
            {
                
            }

(3)  try
            {
                using (SqlConnection conn=new SqlConnection("连接字符串"))
                {
                    conn.Open();
                }
            }
            catch (Exception ex)
            {
                
                throw;
            }

　(1)　用try...catch...finally 能及时关闭数据库,能够抛出异常,

   (2) 用using结构较为简单,不用手工关闭,但不能抛出异常

所以综合两者的优点,两种方式结合使用如(3)