Question

我试图制作一个应用来检查eBay当前的观察者。我使用以下代码找到eBay观察者计数..没问题。然后我使用await asyncro代码修复UI阻塞。

但它正在获取invalidoperationexception是未处理的异常。

        private async void button1_Click(object sender, EventArgs e)
    {
        Task<int> task = new Task<int>(counting);
        task.Start();

        label1.Text = "Please wait";
        await task;

    }

  private int counting()
    {

        string[] idlist = richTextBox1.Text.Split('\n'); // <= getting exception

        // foreach (string id in idlist)
        for (int i = 0; i < Convert.ToInt32(idlist.Length); i++)
        {
            string url = "http://m.ebay.com/itm/" + idlist[i];
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            StreamReader sr = new StreamReader(response.GetResponseStream());
            // richTextBox2.Text += sr.ReadToEnd();
            string a = sr.ReadToEnd();
            sr.Close();




            string number = String.Empty;
            string pattern = @"(?<=""defaultWatchCount""\s*:\s*)\d+";
            string input = a;

            foreach (Match m in Regex.Matches(input, pattern))
            {
                number = m.Value;

            }
            richTextBox2.Text += number + Environment.NewLine;
        }

        return 0;
    }

我对等待和异步了解不多...请问有人可以解决此错误吗？

Answer 1

尝试从与创建线程不同的线程访问UI控件将导致跨线程访问冲突。因此，如果目标是在后台线程上进行网络调用，那么您需要将后台任务与用户界面分开

以下是对原始代码的重构，该原始代码采用ID集合并使用ngOnChanges(changes: SimpleChanges) { this.C_code = this.CartdataService.category_code; this.G_code = this.CartdataService.group_code; this.SG_code = this.CartdataService.subgroup_code; this.CartdataService.get_Selected_Category_Of_Products(this.C_code, this.G_code, this.SG_code).subscribe( (data : any) => { this.size = data.length; this.CartdataService.prooductCountUnderCGS.next(this.size); this.products = data; }); }进行异步Web调用。所有Web调用将在单独的线程上并行完成。

HttpClient

因此，现在在按钮单击处理程序中，您可以在UI线程中启动，将请求卸载到其他线程，并等待它们完成，同时不锁定UI线程。完成后，您将提取返回的值，并根据需要将其传递给

static Lazy<HttpClient> client = new Lazy<HttpClient>(() => {
    string baseUrl = "http://m.ebay.com/itm/";
    var client = new HttpClient() {
        BaseAddress = new Uri(baseUrl)
    };
    return client;
});

private Task<string[]> GetWatchCountsAsync(string[] idlist) {
    string pattern = @"(?<=""defaultWatchCount""\s*:\s*)\d+";
    var tasks = idlist.Select(async id => {
        var input = await client.Value.GetStringAsync(id.Trim());
        string number = String.Empty;
        foreach (Match m in Regex.Matches(input, pattern)) {
            number += m.Value;
        }
        return number;
    });
    return Task.WhenAll(tasks);
}

如何使用RichTextBox使用await和async？

1 个答案:

如何使用RichTextBox使用aw​​ait和async？

1 个答案:

如何使用RichTextBox使用await和async？