mysql中的longblob类型处理

longblob 对应的 C#数据类型为 byte[]

1.byte[] 与 string 之间的转换

　　byte[] bb = Encoding.UTF8.GetBytes(ss);
　　string s = Encoding.UTF8.GetString(bb);

2.byte[] 与 image 之间的转换

        //参数是图片的路径
        public byte[] GetPictureData(string imagePath)
        {
            FileStream fs = new FileStream(imagePath, FileMode.Open);
            byte[] byteData = new byte[fs.Length];
            fs.Read(byteData, 0, byteData.Length);
            fs.Close();
            return byteData;
        }

        //将Image转换成流数据，并保存为byte[] 
        public byte[] PhotoImageInsert(System.Drawing.Image imgPhoto)
        {
            MemoryStream mstream = new MemoryStream();
            imgPhoto.Save(mstream, System.Drawing.Imaging.ImageFormat.Bmp);
            byte[] byData = new Byte[mstream.Length];
            mstream.Position = 0;
            mstream.Read(byData, 0, byData.Length); mstream.Close();
            return byData;
        }

  public static BitmapImage ByteArrayToBitmapImage(byte[] byteArray)
        {
            BitmapImage bmp = null;
            try
            {
                bmp = new BitmapImage();
                bmp.BeginInit();
                bmp.StreamSource = new MemoryStream(byteArray);
                bmp.EndInit();
            }
            catch
            {
                bmp = null;
            }

            return bmp;
        }