文件二进制与String相互转换

           //转换base64
            OpenFileDialog dialog = new OpenFileDialog();
            //dialog.Filter = "所有文件(*.*)|*.*";
            dialog.CheckFileExists = true;
            dialog.ShowDialog();
            if (!string.IsNullOrEmpty(dialog.FileName))
            {
                try
                {
                    byte[] byteArray = FileBinaryConvertHelper.File2Bytes(dialog.FileName);
                    string base64 = Convert.ToBase64String(byteArray);
                    txtContent.Text = base64;
　　　　　　　　　　　 txtContent.Focus();
　　　　　　　　　　　 txtContent.SelectAll();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }    

            //解转换base64 
            SaveFileDialog dialog = new SaveFileDialog();
            dialog.Filter = "所有文件(*.*)|*.*";
            dialog.ShowDialog();
            if (!string.IsNullOrEmpty(dialog.FileName))//可以上传压缩包.zip 或者jar包
            {
                try
                {
                    byte[] byteArray = Convert.FromBase64String(txtContent.Text); 
                    FileBinaryConvertHelper.Bytes2File(byteArray,dialog.FileName);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }

    /// <summary>
    /// 工具类：文件与二进制流间的转换
    /// </summary>
    public class FileBinaryConvertHelper
    {
        /// <summary>
        /// 将文件转换为byte数组
        /// </summary>
        /// <param name="path">文件地址</param>
        /// <returns>转换后的byte数组</returns>
        public static byte[] File2Bytes(string path)
        {
            if (!System.IO.File.Exists(path))
            {
                return new byte[0];
            }

            FileInfo fi = new FileInfo(path);
            byte[] buff = new byte[fi.Length];

            FileStream fs = fi.OpenRead();
            fs.Read(buff, 0, Convert.ToInt32(fs.Length));
            fs.Close();

            return buff;
        }

        /// <summary>
        /// 将byte数组转换为文件并保存到指定地址
        /// </summary>
        /// <param name="buff">byte数组</param>
        /// <param name="savepath">保存地址</param>
        public static void Bytes2File(byte[] buff, string savepath)
        {
            if (System.IO.File.Exists(savepath))
            {
                System.IO.File.Delete(savepath);
            }

            FileStream fs = new FileStream(savepath, FileMode.CreateNew);
            BinaryWriter bw = new BinaryWriter(fs);
            bw.Write(buff, 0, buff.Length);
            bw.Close();
            fs.Close();
        }

txtContent.Focus();                    txtContent.SelectAll();