事务、锁 的问题

[prettyBoy1]

SqlConnection myConnection = new SqlConnection(myConnString);
myConnection.Open();
SqlCommand myCommand = myConnection.CreateCommand();
SqlTransaction myTrans;

// Start a local transaction
myTrans = myConnection.BeginTransaction (IsolationLevel.ReadUncommitted,"SampleTransaction");
// Must assign both transaction object and connection
// to Command object for a pending local transaction
myCommand.Connection = myConnection;
myCommand.Transaction = myTrans;

try
{
myCommand.CommandText = "insert into buser(username,realname) values('sss5','sss5')";
myCommand.ExecuteNonQuery();
myCommand.CommandText = "insert into mywt_mis..buser(username,realname) values('sss6','sss6')";
myCommand.ExecuteNonQuery();
myTrans.Commit();
Console.WriteLine("Both records are written to database.");
}
catch(Exception e)
{
myTrans.Rollback("SampleTransaction");
}
finally
{
myConnection.Close();
}

我的问题是：我想要在事务执行期间，别人仍然可以访问该表，可以用select * from buser来查询该表。我先在用了 级别最低的锁ReadUncommitted，我在中间设置了断电，执行到断点，我用sql 查询分析器, 执行：select * from buser，提示锁超时。 不是说级别低的锁，不锁吗，还可以读脏数据，怎么不能读呢？

[pontus]

插入数据时使用了排它锁，其他事务不能读取或者修改