How to make PNG image with white background transparent using C#

public static byte[] GetTransparentArrayFromFileWithDelete(string pathToFile)
        {
            byte[] newImage = new byte[0]; error = string.Empty;
            using (Bitmap bmp = new Bitmap(pathToFile))
            {
                Color pixel = bmp.GetPixel(0, 0);                               
                if (pixel.A != 0)
                {                    
                    // Make backColor transparent for myBitmap.
                    bmp.MakeTransparent(Color.Transparent);

                    ImageConverter converter = new ImageConverter();
                    newImage = (byte[])converter.ConvertTo(bmp, typeof(byte[]));
                    bmp.Dispose();
                }
                else
                {
                    FileStream fs = new FileStream(pathToFile, FileMode.OpenOrCreate, FileAccess.Read);
                    newImage = new byte[fs.Length];
                    fs.Read(newImage, 0, System.Convert.ToInt32(fs.Length));
                    fs.Close();
                }
            }
            try
            {
                File.Delete(pathToFile);
            }
            catch
            {
            }
            return newImage;
        }