// set a default file
            this.saveFileDialog1.FileName = "untitled.Png";
            // set filters - this can be done in properties as well
            this.saveFileDialog1.Filter = "Png Files (*.Png)|*.Png";
            this.saveFileDialog1.DefaultExt = "Png";
            if (this.saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                Bitmap bitmap = new Bitmap(this.nChartControl2.ClientSize.Width, this.nChartControl2.ClientSize.Height, PixelFormat.Format24bppRgb);
                this.nChartControl2.ImageExporter.RenderToBitmap(bitmap, false);
                bitmap.Save(this.saveFileDialog1.FileName, ImageFormat.Png);
            }