C# Image與Base64編碼互轉函數

        /// <summary>
        /// 根據base64字符串返回一個封裝好的GDI+位圖。
        /// </summary>
        /// <param name="base64string">可轉換成位圖的base64字符串。</param>
        /// <returns>Bitmap對象。</returns>
        public Bitmap GetImageFromBase64(string base64string)
        {
            byte[] b = Convert.FromBase64String(base64string);
            MemoryStream ms = new MemoryStream(b);
            Bitmap bitmap = new Bitmap(ms);
            return bitmap;
        }

        /// <summary>
        /// 將圖片轉換成base64字符串。
        /// </summary>
        /// <param name="imagefile">須要轉換的圖片文件。</param>
        /// <returns>base64字符串。</returns>
        public string GetBase64FromImage(string imagefile)
        {
            string strbaser64 = "";

            try
            {
                Bitmap bmp = new Bitmap(imagefile);
                using (MemoryStream ms = new MemoryStream())
                {
                    bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                    byte[] arr = new byte[ms.Length];
                    ms.Position = 0;
                    ms.Read(arr, 0, (int)ms.Length);
                    ms.Close();

                    strbaser64 = Convert.ToBase64String(arr);
                }
            }
            catch (Exception)
            {
                throw new Exception("Something wrong during convert!");
            }

            return strbaser64;
        }