从 .net 获取 MySql 数据时出错； （命令执行过程中遇到致命错误）

Question

我正在从.Net 应用程序的 MySQL 获取数据。 它有时会抛出错误，如下所示

MySql.Data.MySqlClient.MySqlException (0x80004005): Fatal error encountered during command execution.
---> MySql.Data.MySqlClient.MySqlException (0x80004005): Fatal error encountered attempting to read the resultset.
---> MySql.Data.MySqlClient.MySqlException (0x80004005): Reading from the stream has failed.
---> System.IO.IOException: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
    at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
    at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
    --- End of inner exception stack trace ---
    at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
    at MySql.Data.MySqlClient.TimedStream.Read(Byte[] buffer, Int32 offset, Int32 count)
    at MySql.Data.MySqlClient.MySqlStream.ReadFully(Stream stream, Byte[] buffer, Int32 offset, Int32 count)
    at MySql.Data.MySqlClient.MySqlStream.LoadPacket()
    at MySql.Data.MySqlClient.MySqlStream.LoadPacket()
    at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
    at MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int64& insertedId)
    at MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId, Int32& affectedRows, Int64& insertedId)
    at MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId, Boolean force)
    at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
    at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
    at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
    at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
    at MySql.Data.MySqlClient.MySqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
    at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
    at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
    at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
    at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet)

我的代码如下

_mySqlConn = new MySqlConnection(ConfigurationManager.ConnectionStrings["BiometricConnectionPush"].ToString());
_mySqlConn.Open();
_strQry = "SELECT * FROM biologs WHERE id>" + LastPunchId + " ORDER BY id ASC LIMIT " + RowLimit.ToString();

MySqlCommand _sqlCmd = new MySqlCommand();
_sqlCmd.CommandText = _strQry;
_sqlCmd.CommandTimeout = 100000;
_sqlCmd.Connection = _mySqlConn;
_sqlCmd.CommandType = CommandType.Text;

Data = new DataSet();
_mySqlDa = new MySqlDataAdapter(_sqlCmd);
_mySqlDa.Fill(Data);

Answer 1

System.IO.IOException: Unable to read data from the transport connection: 连接尝试失败，因为连接方在一段时间后没有正确响应，或者建立连接失败，因为连接的主机没有响应。

System.Net.Sockets.SocketException：连接尝试失败，因为连接方在一段时间后没有正确响应，或者连接失败，因为连接的主机没有响应。

无法联系您的 MySQL 服务器，或者事情超时。

请注意，您已将命令超时明确设置为 10 秒； 如果由于某种原因执行您的查询需要更多的时间，您会得到该异常。