例外：已经有与此连接关联的开放的DataReader，必须先关闭 [英] Exception: There is already an open DataReader associated with this Connection which must be closed first

问题描述

下面我有code和我得到异常：

  

有已经是公开的的DataReader 本连接必须先关闭相关联。

我使用Visual Studio 2010 / .NET 4.0和MySQL这个项目。基本上，我试图同时使用数据读取器做我的其他任务运行另一个SQL语句。我正在逐渐线异常 cmdInserttblProductFrance.ExecuteNonQuery（）;

  SQL =SELECT * FROM tblProduct//创建连接/命令/了MySqlDataReader
的MySqlConnection MyConnection的=新的MySqlConnection（cf.GetConnectionString（））;
myConnection.Open（）;
的MySqlCommand myCommand =新的MySqlCommand（SQL，MyConnection的）;
MySqlDataReader将myReader = myCommand.ExecuteReader（）;
myCommand.Dispose（）;如果（myReader.HasRows）
{
    INT I = 0;
    //访问数据之前，请务必调用Read。
    而（myReader.Read（））
    {
        如果（myReader [frProductid]。的ToString（）==）//没有存在的ProductID此项目
        {
            strInsertSQL =INSERT INTO tblProduct_temp（PRODUCTID）VALUES（'这istest'）;
            的MySqlCommand cmdInserttblProductFrance =新的MySqlCommand（strInsertSQL，MyConnection的）;
            cmdInserttblProductFrance.ExecuteNonQuery（）; //＆LT; =====此行抛出C＃的MySQL已经有与此连接，必须先关闭相关联的打开DataReader的。
        }
    }
}
 

解决方案

您正在使用相同的连接的DataReader 和的ExecuteNonQuery 。这是不支持，根据MSDN ：

  

请注意，虽然一个DataReader是开放的，连接在使用
  完全由DataReader的。你不能执行任何命令的
  连接，其中包括创建另一个DataReader的，直到
  原来DataReader关闭。

I have below code and I am getting exception:

There is already an open DataReader associated with this Connection which must be closed first.

I am using Visual Studio 2010/.Net 4.0 and MySQL for this project. Basically I am trying to run another SQL statement while using data reader to do my other task. I am getting exception at line cmdInserttblProductFrance.ExecuteNonQuery();

SQL = "Select * from tblProduct";

//Create Connection/Command/MySQLDataReader
MySqlConnection myConnection = new MySqlConnection(cf.GetConnectionString());
myConnection.Open();
MySqlCommand myCommand = new MySqlCommand(SQL, myConnection);
MySqlDataReader myReader = myCommand.ExecuteReader();
myCommand.Dispose();

if (myReader.HasRows)
{
    int i = 0;
    // Always call Read before accessing data.
    while (myReader.Read())
    {
        if (myReader["frProductid"].ToString() == "") //there is no productid exist for this item
        {
            strInsertSQL = "Insert Into tblProduct_temp (Productid) Values('this istest') ";
            MySqlCommand cmdInserttblProductFrance = new MySqlCommand(strInsertSQL, myConnection);
            cmdInserttblProductFrance.ExecuteNonQuery(); //<=====THIS LINE THROWS "C# mySQL There is already an open DataReader associated with this Connection which must be closed first."
        }
    }
}

解决方案

You are using the same connection for the DataReader and the ExecuteNonQuery. This is not supported, according to MSDN:

Note that while a DataReader is open, the Connection is in use exclusively by that DataReader. You cannot execute any commands for the Connection, including creating another DataReader, until the original DataReader is closed.

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