Например, для webView1 элемента управления в Winforms с пакетом Microsoft.Toolkit.Forms.UI.Controls.WebView :
webView1.NavigationCompleted += new System.EventHandler<Microsoft.Toolkit.Win32.UI.Controls.Interop.WinRT.WebViewControlNavigationCompletedEventArgs>(this.webView1_NavigationCompleted);
и:
private async void GetPageHTML()
{
sHTMLSource = await webView1.InvokeScriptAsync("eval", new string[] { "document.documentElement.outerHTML;" });
}
private string sHTMLSource = null;
private void webView1_NavigationCompleted(object sender, Microsoft.Toolkit.Win32.UI.Controls.Interop.WinRT.WebViewControlNavigationCompletedEventArgs e)
{
GetPageHTML();
}