单项选择题
下面程序下载http://127.0.0.1的字符串： try { WebClient client = new WebClient(); client.Encoding = Encoding.UTF8; client.DownloadStringCompleted += client_DownloadStringCompleted; Uri uri = new Uri("http://127.0.0.1", UriKind.Absolute); client.DownloadStringAsync(uri); msg.Text = "OK"; } catch (Exception exp) { msg.Text = exp.Message; }在执行client.DownloadStringAsync(uri)后
A、程序等待服务器响应，然后显示msg.Text = "OK";
B、程序不等待服务器响应，就显示msg.Text = "OK";
C、程序有错误，语句 client.DownloadStringCompleted += client_DownloadStringCompleted;应该为：client.DownloadStringCompleted = client_DownloadStringCompleted;
D、以上都不对