#region 将文件保存到本地
        /// <summary>
        /// 将文件保存到本地
        /// </summary>
        /// <param name="psContent">文件的二进制数据字符串</param>
        /// <param name="psFileName">文件名称，必须带后缀</param>
        private void SaveFile(string psContent, string psFileName)
        {
            byte[] accessory = Convert.FromBase64String(psContent);
            //System.AppDomain.CurrentDomain.BaseDirectory获取程序的基目录
            string vsAccessoryPath = System.AppDomain.CurrentDomain.BaseDirectory.TrimEnd('\\') + '\\' + psFileName;
            FileStream fileStream = null;
            try
            {
                //File.Create Method (String):Creates or overwrites a file in the specified path.
                fileStream = File.Create(vsAccessoryPath);
            }
            catch (System.IO.IOException e)
            {
                
            }
            //FileStream.Write Method:Writes a block of bytes to the file stream.
            fileStream.Write(accessory, 0, accessory.Length);
            //FileStream.Flush 方法:清除该流的所有缓冲区，使得所有缓冲的数据都被写入到基础设备。
            fileStream.Flush();
            //FileStream.Close Method:Closes the file and releases any resources associated with the current file stream.
            fileStream.Close();
        }
        #endregion

假如文件流保存在数据库中：

string vsSql = "";//从数据库中获取待转换保存文件的内容（比如，之前把文件转换为字节流保存到数据库中了）
DataSet dsContent = 获取DataSet的数据库操作;
byte[] vbContent = (byte[])(dsContent.Tables[0].Rows[0]["数据库中保存文件内容的列名"]);
string vsContent = Convert.ToBase64String(vbContent);

字节流保存在数据库中的样子：