Question

从namespace Download_Extract { public partial class Form1 : Form { public Form1() { InitializeComponent(); } //static EventWaitHandle _ready = new AutoResetEvent(false); //static EventWaitHandle _go = new AutoResetEvent(false); // ***Download and extract*** private void Button1_Click(object sender, EventArgs e) { string BTurl = "https://the/file/is/located/here/self_extracting_7z_file.exe"; string BTlocation = Path.Combine(Path.GetTempPath(), "self_extracting_7z_file.exe"); startDownload(BTurl, BTlocation); //_ready.WaitOne(); //wait here until _ready.Set() is retruned label3.Text = "Extracting Files......."; //_ready.Set() has been received Process.Start(BTlocation, @"-aoa -y -oc:\dest_folder").WaitForExit(); label3.Text = "Extracting Files Completed"; } private void startDownload(string BTurl, string BTlocation) { Thread thread = new Thread(() => { WebClient client = new WebClient(); client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(client_DownloadProgressChanged); client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted); client.DownloadFileAsync(new Uri(BTurl), BTlocation); }); thread.Start(); //_ready.Set(); // test C *ProgressBar works, but doesn't wait for completed dl before continuing } void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e) { this.BeginInvoke((MethodInvoker)delegate { double bytesIn = double.Parse(e.BytesReceived.ToString()); double totalBytes = double.Parse(e.TotalBytesToReceive.ToString()); double percentage = bytesIn / totalBytes * 100; label3.Visible = true; label3.Text = "Downloading.... "; // + e.BytesReceived + " of " + e.TotalBytesToReceive; label10.Visible = true; label10.Text = String.Format("{0:0}", percentage) + "%"; progressBar1.Visible = true; progressBar1.Value = int.Parse(Math.Truncate(percentage).ToString()); }); //_ready.Set(); // test B *ProgressBar works, but doesn't wait for completed dl before continuing } void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e) { this.BeginInvoke((MethodInvoker)delegate { label10.Visible = false; label3.Text = "Download completed."; }); //_ready.Set(); // test A *works, but with issues. pBar delayed, no #%.text shown } } }到元组，再到对象，数字...如果用unknown访问它们，则等于[never]。那么，never为何表现不同？以下是一致的，为什么？

any[never]

Answer 1

我认为这是一致的。 never是所有类型的子类型。因此可以将其分配给任何其他类型。因此，如果我们可以使用never进行索引而不会出现编译器错误：

declare let o: never;
declare let arr: any[];
arr[o] // not error, any

其余的只是可以索引的内容。 number和object没有索引签名，因此结果为never。 string是可索引的，结果是string，因此string[never]是string。 any是通用可索引的，结果是any，所以any[never]是any。

对于如上所述用never进行索引的数组是可能的，并且将为我们提供项目类型，因此这些结果是一致的。

“ any [never]”类型为“ any”是否正确？

1 个答案: