上传图片用图片文件的对象hash哈希值判断图片是否一样，避免重复提交相同的图片到服务器中

 ???????/// <summary> ???????/// 上传企业logo ???????/// </summary> ???????/// <returns></returns> ???????public ActionResult UploadLogo(string comid) ???????{ ???????????HttpFileCollection files = System.Web.HttpContext.Current.Request.Files; ???????????if (files.Count == 0) return Json("没有没文件", JsonRequestBehavior.AllowGet); ???????????MD5 hash = new MD5CryptoServiceProvider(); ???????????/**计算指定stream对象的哈希值**/ ???????????byte[] bytehashValue = hash.ComputeHash(files[0].InputStream); ???????????var HashData = BitConverter.ToString(bytehashValue).Replace("-", ""); ???????????var FileExtension = Path.GetExtension(files[0].FileName); ???????????var filename = comid + "_" + HashData + FileExtension; ???????????var virtualpath = string.Format("/Upload/Logo/{0}/{1}", DateTime.Now.ToString("yyyyMMdd"), filename); ???????????//将虚拟路劲转换成物理路劲 ???????????var fullpath = Server.MapPath(virtualpath); ???????????var path = Path.GetDirectoryName(fullpath); ???????????if (!Directory.Exists(path)) ???????????????Directory.CreateDirectory(path); ???????????if (!System.IO.File.Exists(fullpath)) ???????????????files[0].SaveAs(fullpath); ???????????var FileSize = this.FileSize(files[0].ContentLength); ???????????return Json(new { FileName = filename, FilePath = virtualpath, FileSize = FileSize }, "text/html", JsonRequestBehavior.AllowGet); ???????} ???????/// <summary> ???????/// 计算文件大小 ???????/// </summary> ???????/// <param name="bytes"></param> ???????/// <returns></returns> ???????public string FileSize(long bytes) ???????{ ???????????long kblong = 1024; ???????????long mblong = 1024 * 1024; ???????????if (bytes < kblong) ???????????????return decimal.Round(decimal.Divide(bytes, kblong), 2).ToString() + "KB"; ???????????else ???????????????return decimal.Round(decimal.Divide(bytes, mblong), 2).ToString() + "MB"; ???????}

 ???????/// <summary> ???????/// 计算文件的hash值 用于比较两个文件是否相同 ???????/// </summary> ???????/// <param name="filePath">文件路径</param> ???????/// <returns>文件hash值</returns> ???????public static string GetFileHash(string filePath) ???????{ ???????????//创建一个哈希算法对象 ????????????using (HashAlgorithm hash = HashAlgorithm.Create()) ???????????{ ???????????????using (FileStream file = new FileStream(filePath, FileMode.Open)) ???????????????{ ???????????????????//哈希算法根据文本得到哈希码的字节数组 ????????????????????byte[] hashByte= hash.ComputeHash(file); ???????????????????//将字节数组装换为字符串 ?????????????????????return BitConverter.ToString(hashByte); ???????????????} ???????????} ???????}