c# - How to take a screenshot of a WPF control?

Question

I created a WPF application using the Bing maps WPF control. I would like to be able to screenshot only the Bing maps control.

Is use this code to make the screenshot:

// Store the size of the map control
int Width = (int)MyMap.RenderSize.Width;
int Height = (int)MyMap.RenderSize.Height;
System.Windows.Point relativePoint = MyMap.TransformToAncestor(Application.Current.MainWindow).Transform(new System.Windows.Point(0, 0));
int X = (int)relativePoint.X;
int Y = (int)relativePoint.Y;

Bitmap Screenshot = new Bitmap(Width, Height);
Graphics G = Graphics.FromImage(Screenshot);
// snip wanted area
G.CopyFromScreen(X, Y, 0, 0, new System.Drawing.Size(Width, Height), CopyPixelOperation.SourceCopy);

string fileName = "C:\myCapture.bmp";
System.IO.FileStream fs = System.IO.File.Open(fileName, System.IO.FileMode.OpenOrCreate);
Screenshot.Save(fs, System.Drawing.Imaging.ImageFormat.Bmp);
fs.Close();

My problem:

The Width and Height appear to be bad (false values). The screenshot produced appear to use bad coordinates.

My screenshot:

What I expect:

Why do I get this result? I tried in Release mode, and without Visual Studio, result is the same.

Answer 1

A screenshot is a shot of the screen... everything on the screen. What you want is to save an image from a single UIElement and you can do that using the RenderTargetBitmap.Render Method. This method takes a Visual input parameter and luckily, that is one of the base classes for all UIElements. So assuming that you want to save a .png file, you could do this:

RenderTargetBitmap renderTargetBitmap = 
    new RenderTargetBitmap(width, height, 96, 96, PixelFormats.Pbgra32);
renderTargetBitmap.Render(yourMapControl); 
PngBitmapEncoder pngImage = new PngBitmapEncoder();
pngImage.Frames.Add(BitmapFrame.Create(renderTargetBitmap));
using (Stream fileStream = File.Create(filePath))
{
    pngImage.Save(fileStream);
}