Boolean fileOk = false;          string path = Server.MapPath("~/images/");          //判斷是否已經選取文件          if (FileUpload1.HasFile)          {              //取得文件的擴展名,并轉換成小寫              string fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower();              //限定只能上傳jpg和gif圖片              string[] allowExtension = { ".jpg", ".gif" };              //對上傳的文件的類型進行一個個匹對              int j = 0;              for (int i = 0; i < allowExtension.Length; i++)              {                  if (fileExtension == allowExtension[i])                  {                      fileOk = true;                      return;                  }                  else                  {                      j++;                  }              }              if (j > 0)              {                  Response.Write("<scr

Boolean fileOk = false;           string path = Server.MapPath("~/images/");           //判斷是否已經選取文件           if (FileUpload1.HasFile)           {               //取得文件MIME內容類型               string type = this.FileUpload1.PostedFile.ContentType.ToLower();               if (type.Contains("image"))    //圖片的MIME類型為"image/xxx"，這里只判斷是否圖片。               {                   fileOk = true;                }               else               {                   Response.Write("<script>alert('格式不正確')</script>");               }           }           else           {               Response.Write("<script>alert('你還沒有選擇文件');</script>");           }           //如果擴展名符合條件，則上傳           if (fileOk)           {               FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName);               Response.Write("<script>alert('上傳成功');</script>");           }

try            {                //判斷是否已經選取文件                if (FileUpload1.HasFile)                {                    if (IsAllowedExtension(FileUpload1))                    {                        string path = Server.MapPath("~/images/");                        FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName);                        Response.Write("<script>alert('上傳成功');</script>");                    }                    else                    {                        Response.Write("<script>alert('您只能上傳jpg或者gif圖片');</script>");                    }                 }                else                {                    Response.Write("<script>alert('你還沒有選擇文件');</script>");                }            }            catch (Exception error)            {                Response.Write(error.ToString());            }            #endregion        }//真正判斷文件類型的關鍵函數        public static bool IsAllowedExtension(FileUpload hifile)        {            System.IO.FileStream fs = new System.IO.FileStream(hifile.PostedFile.FileName, System.IO.FileMode.Open, System.IO.Fileaccess.Read);            System.IO.BinaryReader r = new System.IO.BinaryReader(fs);            string fileclass = "";            //這里的位長要具體判斷.            byte buffer;            try            {                buffer = r.ReadByte();                fileclass = buffer.ToString();                buffer = r.ReadByte();                fileclass += buffer.ToString();             }            catch            {             }            r.Close();            fs.Close();            if (fileclass == "255216" || fileclass == "7173")//說明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar            {                return true;            }            else            {                return false;            }         }