为什么我的 using 语句没有关闭连接?

Well, lots of developers on stackoverflow are saying that I should not worry to close my connection: my using statement will close the connection for me, here and here and all over the site. Unfortunately, I do not see it happening. Here is my code:

    [Test, Explicit]
    public void ReconnectTest()
    {
        const string connString = "Initial Catalog=MyDb;Data Source=MyServer;Integrated Security=SSPI;Application Name=ReconnectTest;";
        for (int i = 0; i < 2000; i++)
        {
            try
            {
                using (var conn = new SqlConnection(connString))
                {
                    conn.Open();
                    using (var command = conn.CreateCommand())
                    {
                        command.CommandText = "SELECT 1 as a";
                        command.CommandType = CommandType.Text;
                        command.ExecuteNonQuery();
                    }
                    //conn.Close();
// optional breakpoint 1 below
                    }
                }
                catch(SqlException e)
                {
// breakpoint 2 below
                    Console.WriteLine(e);
                }
// breakpoint 3 below
            }
        }

当我启用所有断点并开始测试时，第一次迭代成功，我遇到了断点 3.此时，连接仍然打开:我在 Profiler 中看到它，并且 sp_who2 也输出了它.