Filnavn uden filtype?

Kode 

        private void button3_Click(object sender, EventArgs e)
        {
            ImageFormat aFormat = new ImageFormat(ImageFormat.Jpeg.Guid);//standard format.
            saveFileDialog1.Title = "Gem fil";
            string extension = ".jpg";
            if (jpegRadio.Checked == true)
            {
                saveFileDialog1.Filter = "JPEG Filer|*.jpg";
                saveFileDialog1.DefaultExt = "*.jpg";
                aFormat = ImageFormat.Jpeg;
                extension = ".jpg";
            }
            else if (PNGRadio.Checked == true)
            {
                saveFileDialog1.Filter = "PNG Filer|*.png";
                saveFileDialog1.DefaultExt = "*.png";
                aFormat = ImageFormat.Png;
                extension = ".png";
            }
            else if (BMPRadio.Checked == true)
            {
                saveFileDialog1.Filter = "BMP Filer|*.bmp";
                saveFileDialog1.DefaultExt = "*.bmp";
                aFormat = ImageFormat.Bmp;
                extension = ".bmp";
            }

            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                /*
                 * Save in the format selected by user in the Radiogroup */
                string newPath = System.IO.Path.ChangeExtension(saveFileDialog1.FileName, extension);
                pictureBox1.Image.Save(newPath, aFormat);
            }
        }   
    }

Kode 

//OutputPath = C:\\hej\\hej.jpg
string[] splitted = outputPath.Split(".".ToCharArray());
splitted[splitted.Length - 1].ToString().ToLower();
//Giver jpg