这是手册中给出的示例。当我尝试同样的方法时,我会遇到无数异常。这有什么错误。
using(NpgsqlConnection conn = new NpgsqlConnection("connstring"))
{
conn.Open();
using(NpgsqlCommand command = new NpgsqlCommand("select command", conn))
{
command.Parameters.Add(new NpgsqlParameter("column1", NpgsqlDbType.Integer);
command.Parameters[0].Value = 4;
using(NpgsqlDataReader dr = command.ExecuteReader())
{
dr.Read();
Console.Write("{0} \t", dr[0]);
}
}
}
例外 :
System exception System.IO.IOException: I/O error occurred.
at Npgsql.NpgsqlState.<ProcessBackendResponses_Ver_3>d__a.MoveNext()
at Npgsql.NpgsqlState.IterateThroughAllResponses(IEnumerable`1 ienum)
at Npgsql.NpgsqlState.Query(NpgsqlConnector context, NpgsqlCommand command)
at Npgsql.NpgsqlConnector.Query(NpgsqlCommand queryCommand)
at Npgsql.NpgsqlConnector.ReleaseRegisteredListen()
at Npgsql.NpgsqlConnector.ReleaseResources()
at Npgsql.NpgsqlConnectorPool.UngetPooledConnector(NpgsqlConnection Connection, NpgsqlConnector Connector)
at Npgsql.NpgsqlConnectorPool.ReleasePooledConnectorInternal(NpgsqlConnection Connection, NpgsqlConnector Connector)
at Npgsql.NpgsqlConnectorPool.ReleasePooledConnector(NpgsqlConnection Connection, NpgsqlConnector Connector)
at Npgsql.NpgsqlConnectorPool.ReleaseConnector(NpgsqlConnection Connection, NpgsqlConnector Connector)
at Npgsql.NpgsqlConnection.Close()
at Npgsql.NpgsqlConnection.Dispose(Boolean disposing)
at System.ComponentModel.Component.Dispose()
现在这可以正常工作。有什么不同 :
using(NpgsqlConnection conn = new NpgsqlConnection("connstring"))
{
conn.Open();
using(NpgsqlCommand command = new NpgsqlCommand("select command", conn))
{
command.Parameters.Add(new NpgsqlParameter("column1", NpgsqlDbType.Integer);
command.Parameters[0].Value = 4;
NpgsqlDataReader dr = command.ExecuteReader();
dr.Read();
Console.Write("{0} \t", dr[0]);
}
}
为什么 datareader 不能与 Idisposable 一起使用?