It's certainly possible to grab a screenshot using the .NET Framework. The simplest way is to create a new Bitmap object and draw into that using the Graphics.CopyFromScreen method.
Sample code:
using (Bitmap bmpScreenCapture = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
Screen.PrimaryScreen.Bounds.Height))
using (Graphics g = Graphics.FromImage(bmpScreenCapture))
{
g.CopyFromScreen(Screen.PrimaryScreen.Bounds.X,
Screen.PrimaryScreen.Bounds.Y,
0, 0,
bmpScreenCapture.Size,
CopyPixelOperation.SourceCopy);
}
Caveat: This method doesn't work properly for layered windows. Hans Passant's answer here explains the more complicated method required to get those in your screen shots.