Question

C# SelectCommand 求解每一行注释

public static DataTable Select(SqlParameter[] SqlParameter, string CommandText)
{
SqlConnection conn = new SqlConnection();
conn.ConnectionString = SqlConnStr.ReturnStr(); // 连接数据库
SqlDataAdapter ad = new SqlDataAdapter();
ad.SelectCommand = new SqlCommand();
ad.SelectCommand.Connection = conn;
ad.SelectCommand.CommandType = CommandType.StoredProcedure;
ad.SelectCommand.CommandText = CommandText;
DataTable dt = new DataTable();
try
{
conn.Open();
ad.Fill(dt);
conn.Close();
}
catch (SqlException ex)
{
throw new Exception("检索数据发生错误", ex);
}

finally
{
if (conn.State == ConnectionState.Open)
conn.Close();
}

return dt;
}

Answer 1

建议你在这之前学习一下通过适配器(SqlDataAdapter)进行数据库操作的流程.

这个不在这里讲解了.

/// <summary>
        /// 从数据库查找数据
        /// </summary>
        /// <param name="SqlParameter">查找数据库的条件</param>
        /// <param name="CommandText"></param>
        /// <returns></returns>
        public static DataTable Select(SqlParameter[] SqlParameter, string CommandText)
        {
            //初始化数据库连接SqlConnection 
            SqlConnection conn = new SqlConnection();
            //获取数据库连接字符串,并赋值给数据库连接.
            //SqlConnStr是一个自己写的类,你去你的代码里找吧.
            conn.ConnectionString = SqlConnStr.ReturnStr();
            //初始化数据库适配器SqlDataAdapter 
            SqlDataAdapter ad = new SqlDataAdapter();
            //初始化数据库适配器的指令SqlCommand
            ad.SelectCommand = new SqlCommand();
            //为指令配置数据库连接
            ad.SelectCommand.Connection = conn;
            //设置通过存储过程进行查找.
            ad.SelectCommand.CommandType = CommandType.StoredProcedure;
            //设置指令的SQL语句.
            ad.SelectCommand.CommandText = CommandText;
            //初始化一个DataTable,用于保存查询结果.
            DataTable dt = new DataTable();
            //try,catch,用于处理异常.
            try
            {
                //打开数据库连接.
                conn.Open();
                //适配器将符合要求的结果装入DataTable中.
                ad.Fill(dt);
                //关闭数据库连接.
                conn.Close();
            }
            //发生错误后执行的代码.
            catch (SqlException ex)
            {
                //人工抛出异常.
                throw new Exception("检索数据发生错误", ex);
            }

            //最后要执行的内容
            finally
            {
                //如果数据库连接处于打开状态,则关闭数据库连接.
                if (conn.State == ConnectionState.Open)
                    conn.Close();
            }
            //返回数据库查询结果DataTable
            return dt;
        }