Dim bm As New RenderTargetBitmap(CInt(c1Chart1.ActualWidth), CInt(c1Chart1.ActualHeight), 96, 96, PixelFormats.[Default])

bm.Render(c1Chart1)

Dim enc As New PngBitmapEncoder()

enc.Frames.Add(BitmapFrame.Create(bm))

Dim fs As New FileStream("chart.png", FileMode.Create)

enc.Save(fs)

RenderTargetBitmap bm = new RenderTargetBitmap(

      (int)c1Chart1.ActualWidth,(int)c1Chart1.ActualHeight,

        96, 96, PixelFormats.Default);

bm.Render(c1Chart1);

PngBitmapEncoder enc = new PngBitmapEncoder();

enc.Frames.Add(BitmapFrame.Create(bm));

FileStream fs = new FileStream("chart.png", FileMode.Create);

enc.Save(fs);