当尝试在SqlDataReader上调用Close或Dispose时,我得到一个超时过期的异常。如果您有SQL Server的DbConnection,则可以使用以下命令自行复制:
String CRLF = "\r\n";
String sql =
"SELECT * " + CRLF +
"FROM (" + CRLF +
" SELECT (a.Number * 256) + b.Number AS Number" + CRLF +
" FROM master..spt_values a," + CRLF +
" master..spt_values b" + CRLF +
" WHERE a.Type = 'p'" + CRLF +
" AND b.Type = 'p') Numbers1" + CRLF +
" FULL OUTER JOIN (" + CRLF +
" SELECT (print("code sample");a.Number * 256) + b.Number AS Number" + CRLF +
" FROM master..spt_values a," + CRLF +
" master..spt_values b" + CRLF +
" WHERE a.Type = 'p'" + CRLF +
" AND b.Type = 'p') Numbers2" + CRLF +
" ON 1=1";
DbCommand cmd = connection.CreateCommand();
cmd.CommandText = sql;
DbDataReader rdr = cmd.ExecuteReader();
rdr.Close();
如果你调用reader.Close()或reader.Dispose(),它将抛出一个System.Data.SqlClient.SqlException:
答案 0 :(得分:13)
这是因为您刚刚打开数据阅读器并且尚未完全迭代它。在尝试关闭尚未完成的数据读取器(以及DbConnection)之前,您需要.Cancel()您的DbCommand对象。当然,通过.Cancel() - 你的DbCommand,我不确定这个,但你可能会遇到其他一些例外。但如果它发生,你应该抓住它。
答案 1 :(得分:2)
Cruizer得到了答案:call command.Cancel():
using (DbCommand cmd = connection.CreateCommand())
{
cmd.CommandText = sql;
using (DbDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
if (WeShouldCancelTheOperation())
{
cmd.Cancel();
break;
}
}
}
}
知道你可以调用取消也很有帮助,即使读者已经读过所有行(即它没有抛出一些“没有取消”异常。)
DbCommand cmd = connection.CreateCommand();
try
{
cmd.CommandText = sql;
DbDataReader rdr = cmd.ExecuteReader();
try
{
while (rdr.Read())
{
if (WeShouldCancelTheOperation())
break;
}
cmd.Cancel();
}
finally
{
rdr.Dispose();
}
}
finally
{
cmd.Dispose();
}
答案 2 :(得分:0)
你在哪里读到数据?你只是在创建一个阅读器,但不是在阅读数据。这只是一个猜测,但如果你不读书,读者可能会有问题;)
DbDataReader rdr = cmd.ExecuteReader();
while(rdr.Read())
{
int index = rdr.GetInt32(0);
}