upload上传单张图片

protected void btnpic_upload_Click(object sender, EventArgs e)  {    #region 上传文件   Boolean fileOk = false;   if (pic_upload.HasFile)//验证是否包含文件   {    //取得文件的扩展名,并转换成小写    string fileExtension = Path.GetExtension(pic_upload.FileName).ToLower();    //验证上传文件是否图片格式    fileOk = IsImage(fileExtension);    if (fileOk)    {     //对上传文件的大小进行检测，限定文件最大不超过8M     if (pic_upload.PostedFile.ContentLength < 8192000)     {      string filepath = "~/Admin/I_Institution/Images/";      if (Directory.Exists(Server.MapPath(filepath)) == false)//如果不存在就创建file文件夹      {       Directory.CreateDirectory(Server.MapPath(filepath));      }      string virpath = filepath + CreatePasswordHash(pic_upload.FileName, 4) + fileExtension;//这是存到服务器上的虚拟路径      string mappath = Server.MapPath(virpath);//转换成服务器上的物理路径      pic.Visible = true;      pic_upload.PostedFile.SaveAs(mappath);//保存图片      //显示图片      pic.ImageUrl = virpath;      lbl_pic.Visible = true;      //清空提示      lbl_pic.Text = "上传成功";     }     else     {      pic.Visible = false;      lbl_pic.Visible = true;      pic.ImageUrl = "";      lbl_pic.Text = "文件大小超出8M！请重新选择！";     }    }    else    {     lbl_pic.Visible = false;     pic.ImageUrl = "";     lbl_pic.Text = "要上传的文件类型不对！请重新选择！";    }   }   else   {    lbl_pic.Visible = false;    pic.ImageUrl = "";    lbl_pic.Text = "请选择要上传的图片！";   }   #endregion  }  /// <summary>  /// 验证是否指定的图片格式  /// </summary>  /// <param name="str"></param>  /// <returns></returns>  public bool IsImage(string str)  {   bool isimage = false;   string thestr = str.ToLower();   //限定只能上传jpg和gif图片   string[] allowExtension = { ".jpg", ".gif", ".bmp", ".png" };   //对上传的文件的类型进行一个个匹对   for (int i = 0; i < allowExtension.Length; i++)   {    if (thestr == allowExtension[i])    {     isimage = true;     break;    }   }   return isimage;  }  /// <summary>  /// 创建一个指定长度的随机salt值  /// </summary>  public string CreateSalt(int saltLenght)  {   //生成一个加密的随机数   RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();   byte[] buff = new byte[saltLenght];   rng.GetBytes(buff);   //返回一个Base64随机数的字符串   return Convert.ToBase64String(buff);  }  /// <summary>  /// 返回加密后的字符串  /// </summary>  public string CreatePasswordHash(string pwd, int saltLenght)  {   string strSalt = CreateSalt(saltLenght);   //把密码和Salt连起来   string saltAndPwd = String.Concat(pwd, strSalt);   //对密码进行哈希   string hashenPwd = FormsAuthentication.HashPasswordForStoringInConfigFile(saltAndPwd, "sha1");   //转为小写字符并截取前16个字符串   hashenPwd = hashenPwd.ToLower().Substring(0, 16);   //返回哈希后的值   return hashenPwd;  }

tr>      <td height="25" width="30%" align="right">       机构图标路径 ：      </td>      <td height="25" width="*" align="left">       <asp:Image ID="pic" runat="server" Width="200px" Visible="False" /><br />       <asp:FileUpload ID="pic_upload" runat="server" />       <asp:Button ID="btnpic_upload" runat="server" Text="图片开始上传" OnClick="btnpic_upload_Click" /><br />       <asp:Label ID="lbl_pic" runat="server" Text="" Visible="False"></asp:Label>      </td>     </tr>