WebClient重试

Question

是否可以重试webclient请求？偶尔，我的应用程序会在尝试连接到xml服务时抛出错误，但如果我重试，它可以正常工作。我希望它在抛出错误之前重试2次，除非有人有更好的解决方案:)

private void ApplicationBarLogin_Click(object sender, EventArgs e)
        {
            settings.UsernameSetting = Username.Text;
            if (RememberPassword.IsChecked == true)
            {
                settings.PasswordSetting = Password.Password;
                settings.RememberPasswordSetting = true;
            }
            else
            {
                settings.RememberPasswordSetting = false;
            }

            WebClient internode = new WebClient();

            internode.Credentials = new NetworkCredential(settings.UsernameSetting, settings.PasswordSetting);
            internode.DownloadStringCompleted += new DownloadStringCompletedEventHandler(internode_DownloadStringCompleted);
            internode.DownloadStringAsync(new Uri("https://customer-webtools-api.internode.on.net/api/v1.5/"));
        }

        public void internode_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
            }
            else
            {
                MessageBox.Show("Authentication successfull.");
            }
        }

Answer 1

如果你得到一个失败，你可以重新发出请求。通过对重新发出请求的次数进行计数，可以确定何时向用户显示错误。以下是对代码的快速修改，以演示我的意思。

private void ApplicationBarLogin_Click(object sender, EventArgs e)
{
    settings.UsernameSetting = Username.Text;
    if (RememberPassword.IsChecked == true)
    {
        settings.PasswordSetting = Password.Password;
        settings.RememberPasswordSetting = true;
    }
    else
    {
        settings.RememberPasswordSetting = false;
    }

    WebClient internode = new WebClient();

    internode.Credentials = new NetworkCredential(settings.UsernameSetting, settings.PasswordSetting);
    internode.DownloadStringCompleted += new DownloadStringCompletedEventHandler(internode_DownloadStringCompleted);
    internode.DownloadStringAsync(new Uri("https://customer-webtools-api.internode.on.net/api/v1.5/"));
}

private int _retryCount = 0;

public void internode_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    if (e.Error != null)
    {
        _retryCount++;
        if (_retryCount < 3)
        {
            WebClient internode = (WebClient)sender;
            internode.DownloadStringAsync(new Uri("https://customer-webtools-api.internode.on.net/api/v1.5/"));
        }
        else
        {
            _retryCount = 0;
            MessageBox.Show(e.Error.Message);
        }
    }
    else
    {
        _retryCount = 0;
        MessageBox.Show("Authentication successfull.");
    }
}

Answer 2

WebClient没有任何内置的重试功能。

在将问题告知用户之前，您应该自己构建重试逻辑。