public partial class Form1 : Form
{
WebBrowser wb = new WebBrowser();
public Form1()
{
InitializeComponent();
wb.Height = 100;
wb.Width = 100;
wb.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(wb_DocumentCompleted);
}

void wb_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
Bitmap bmp = new Bitmap(100, 100);
wb.DrawToBitmap(bmp, new Rectangle(wb.Location.X, wb.Location.Y, wb.Width, wb.Height));
this.pictureBox1.BackgroundImage = bmp;
}
}
ที่มา: http://thepursuitofalife.com/the-missing-drawtobitmap-function-in-the-net-webbrowser-class/