private void OnDownloadHtmlCompleted(object sender, DownloadHtmlCompletedEventArgs e)
{
string html = e.Html;
progressBar1.Value = progressBar1.Maximum;
progressBar1.Style = ProgressBarStyle.Blocks;
button1.Enabled = true;
button2.Enabled = true;
}
public void DownloadHtmlAsync(Uri address) // 外部调用的入口
{
new DownloadHtmlCallback((Uri uri, AsyncOperation op) => // 下载函数
{
string html = InternalDownload(uri);
DownloadHtmlCompletedEventArgs e = new DownloadHtmlCompletedEventArgs(null, false, html);
op.PostOperationCompleted(DownloadHtmlCompletedCallback, e); // 下载完成后，调用complete函数，关联comple函数和e
}).BeginInvoke(address, AsyncOperationManager.CreateOperation(null), null, null); // 调用async下载函数，关联async函数和和asyncOperation
}