c# - Try-catch 不等待内部的异步函数

Question

我想做的是，在重试下载文件 5 次后，如果由于某种原因下载失败，重置整个过程并返回第一步:函数 Try() 。如果成功，则继续 ProcessSet(3); 行

但在我的情况下，它开始下载，无需等待，就进入 ProcessSet(3); 行。

我做错了什么？为什么 try 之后的后续步骤不等待 await webClient.DownloadFileTaskAsync(new Uri(response.Url), zip_path); 完成？

这是代码:

using (WebClient webClient = new WebClient())
{
    webClient.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;

    try
    {
        await webClient.DownloadFileTaskAsync(new Uri(response.Url), zip_path);
    }
    catch (Exception e)
    {
        Thread.Sleep(DelayOnRetry);
        Try();
    }
}
SetProgressBar(40, ProgressBarStyle.Continuous);
ProcessSet(3);

这是 Try() 函数

private void Try()
{
    ClearFolder(root_dir);
    Directory.CreateDirectory(root_dir);
    main_timer.Enabled = false;
    ProcessSet(1);
}

这是完整的代码:

https://gist.github.com/turalus/8c781b5b0c56f66f7ec17e66a3e120fc

Answer 1

我建议您更改重试逻辑:

var isFileDownloaded = false;
var tryCount = 0;
while (tryCount++ < MAX_TRY_COUNT && !isFileDownloaded) {
     using (WebClient webClient = new WebClient())
     try{
         //do stuff here
         isFileDownloaded = true
     }catch //log exception and Thread.Sleep

}

if (isFileDownloaded){
//        update progress
} else{
//too many retries, exit app
}