当我同时有多个DBDataReaders读取数据时，我收到以下错误：
There is already an open DataReader associated with this Connection which must be
closed first
我在我的配置中启用了 ConnectionPooling，所以我不明白为什么会收到此错误。由于我当前的连接已经在使用中，它不应该创建一个新连接吗？
我知道设置MultipleActiveResultSets为 true 可以解决问题，但我仍在尝试了解问题存在的原因
Connection pooling does not do what you think it does.
If you do something like this
var connection = new SqlConnection(connectionString);
connection.Open();
var command = connection.CreateCommand();
command.CommandText = // some query
var reader = command.ExecuteReader();
var anotherCommand = connection.CreateCommand();
anotherCommand.CommandText = // another query
var anotherReader = anotherCommand.ExecuteReader();
then all of this will happen on one connection, whether or not you have connection pooling.
Connection pooling just keeps a cache of connections that you can draw from every time that you create a new connection (new SqlConnection) and open it (SqlConnectinon.Open). When you close a connection, it returns to the pool to be reused. But one open SqlConnection object corresponds to one connection from the pool. Period.