Question

我正在获取html源代码并解析它。之后，我想下载图像。我下载它们。但有时候不下载。因为我不能使用我需要的线程或并行编程，我不知道。我的来源是：

foreach(var pic in pics)
        {
            try { 
             client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);
                client.DownloadFileAsync(new Uri(pic.Attributes[cmbAttr.Text].Value), folder + "\\" + picid.ToString() + ".jpg");

            System.Threading.Thread.Sleep(1500); // I wrote sleep code, because i dont know parallel programming. But sometimes it is not downloading in 1500 milisecond.

            picid++;
            }catch(Exception err)
            {
                label8.Text=(err.Message.ToString());
                continue;
            }
        }

这是我的代码。我想按顺序下载图片。 1.jpg，2.jpg等我也下载了它。但有时它会出错。因为另一个下载开始，而上次下载之前完成。我想在完成上次下载后开始。我的英语不好。我希望我说的是真的。感谢帮助。

Answer 1

client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);

foreach(var pic in pics)
{
    Task.Factory.StartNew(Object state =>
    {

        var data = (dynamic)state;
        Int32 id = (Int32)state.Id;
        Picture picture = (Picture)state.Picture;

        client.DownloadFile(new Uri(picture.Attributes[cmbAttr.Text].Value), folder + "\\" + id.ToString() + ".jpg")

    }, new { Id = picid, Picture = pic });

    ++picid;
}

从网址顺序下载图片

1 个答案: