C#webBrowser控件网页加载的问题

webBrowser2_DocumentCompleted不能正常运行，为什么呢，加载完B1后一点反应都没有
private void button1_Click(object sender, EventArgs e)
{
webBrowser1.Navigate(A1);
}

private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e1)
{
if (e1.Url != webBrowser1.Document.Url)
{}
else
{
webBrowser1.Visible = false;
webBrowser2.Visible = true;
webBrowser2.Navigate(B1);

}

}

private void webBrowser2_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e2)
{
if (e2.Url != webBrowser2.Document.Url)
{ }
else
{
MessageBox.Show("加载完B1");
}

}

WebBrowser 的url 你是如何设置的？