SqlDataReader 和 SqlCommand-C#/.NET问题

SqlDataReader and SqlCommand(SqlDataReader 和 SqlCommand)

本文介绍了SqlDataReader 和 SqlCommand的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有以下代码.

using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
{
   connection.Open();
   SqlCommand select = new SqlCommand("SELECT RTRIM(LTRIM(PART_NO)) AS PART_NO, record FROM [RMAData].[dbo].[IMPORTING_ORDER_EDI] WHERE sessionID = '" + Session.SessionID + "'", connection);

   SqlDataReader reader = select.ExecuteReader();

   if (reader.HasRows)
   {
      while (reader.Read())
      {
         if (!currentPart.IsActive)
         {
            // this part is not active, set the active flag in sql to 0
            SqlCommand update = new SqlCommand("UPDATE [RMAData].[dbo].[IMPORTING_ORDER_EDI] SET valid = 0, active = 0 WHERE record = " + reader["record"].ToString() + ";", connection);

            update.ExecuteNonQuery();
         }
         else
         {
            ///blah
         }
      }

      reader.Close();
   }
}

但这会导致以下异常...

but this causes the following exception...

System.InvalidOperationException: 已经有一个打开的 DataReader与必须先关闭的此命令相关联.

我需要读取返回的每一行，对数据进行一些验证并在必要时进行更新，然后继续下一条记录.如果在循环 reader.Read() 时不能使用 SqlCommand ，我该如何实现?

I need to read each row returned, do some validation on the data and make an update if necessary, then continue to the next record. How can I achieve this if I can't use a SqlCommand while looping through reader.Read() ?

推荐答案

另一种方法是不添加 MultipleActiveResultSets=True - 这样做会有一点性能损失 - 所以像这样:

An alternative is not add MultipleActiveResultSets=True - there is a small performance penalty for doing so - and so something like this:

using (SqlConnection connection = new ...))
{
   connection.Open();
   SqlCommand select = new SqlCommand(...);

   SqlDataReader reader = select.ExecuteReader();

   var toInactivate = new List<string>();

   if (reader.HasRows)
   {
      while (reader.Read())
      {
         if (!currentPart.IsActive)
         {
            toInactivate.Add(reader["record"].ToString());
         }
         else
         {
            ///blah
         }
      }

      reader.Close();
   }

   SqlCommand update = new SqlCommand("UPDATE ... SET valid = 0, active = 0 " +
       "WHERE record IN(" + string.Join(",", toInactivate) +  ");", connection);

   update.ExecuteNonQuery();
}

它的优点是在单个 SQL 语句中更新所有必需的记录.

which has the advantage of updating all the required records in a single SQL statement.

当然，如果使用 EF 和 Linq，整个事情会变得更加整洁.

And of course the whole thing would be so much neater using EF and Linq.

这篇关于SqlDataReader 和 SqlCommand的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！