You can use the .NET WebBrowser control to take thumbnails or full-size screenshots of loaded web pages, and then use the Bitmap class to save them locally.

For example, to generate a thumbnail, use:

public Bitmap GenerateThumbnail(string url){    //rendered at full size    return GenerateScreenshot(url, -1, -1);}public Bitmap GenerateThumbnail(string url, int width, int height){    // Load the webpage into a WebBrowser control    WebBrowser wb = new WebBrowser();    wb.ScrollBarsEnabled = false;    wb.ScriptErrorsSuppressed = true;    wb.Navigate(url);    while (wb.ReadyState != WebBrowserReadyState.Complete) {   Application.DoEvents(); }    // Set the size of the WebBrowser control    wb.Width = width;    wb.Height = height;    if (width == -1)    {        // Take Screenshot of the web pages full width        wb.Width = wb.Document.Body.ScrollRectangle.Width;    }    if (height == -1)    {        // Take Screenshot of the web pages full height        wb.Height = wb.Document.Body.ScrollRectangle.Height;    }    // Get a Bitmap representation of the webpage as it's rendered in the WebBrowser control    Bitmap bitmap = new Bitmap(wb.Width, wb.Height);    wb.DrawToBitmap(bitmap, new Rectangle(0, 0, wb.Width, wb.Height));    wb.Dispose();    return bitmap;} 

Here are a couple of examples of calling the preceding code:

// Generate thumbnail of www.devx.com at 1024x768 resolutionBitmap thumbnail = GenerateThumbnail("http://www.devx.com", 1024, 768);// Generate thumbnail of a www.devx.com at full sizethumbnail = GenerateThumbnail("http://www.devx.com");