C#实现文件上传与下载功能实例

<form name="form1" method="post" action="uploadfile.aspx" id="form1"  
enctype="multipart/form-data"> 
  <input type="file" id="txtfile" name="picfile" /></br> 
  <input type="submit" value="上传" /> 
</form> 

random rnd = new random();              //产生随机数 
private string _directory = @"/file/uploadfile";   //目录 
protected void page_load(object sender, eventargs e) 
{ 
  try 
  { 
    if (requestfilescount > 0) 
    { 
      //判断文件大小 
      int length = requestfiles[0]contentlength; 
      if (length > 1048576) 
      { 
        responsewrite("文件大于1m，不能上传"); 
        return; 
      } 
 
      string type = requestfiles[0]contenttype; 
      string fileext = pathgetextension(requestfiles[0]filename)tolower(); 
      //只能上传图片，过滤不可上传的文件类型 
      string filefilt = "gif|jpg|php|jsp|jpeg|png|"; 
      if (filefiltindexof(fileext) <= -1) 
      { 
        responsewrite("对不起！请上传图片！！"); 
        return; 
      } 
      else 
      { 
        string filename = servermappath(_directory) + "\\" + datetimenowtostring("yyyymmddhhmmssfff") + rndnext(10, 99)tostring() + fileext; 
        requestfiles[0]saveas(filename); 
        responsewrite("上传成功！"); 
      } 
    } 
  } 
  catch 
  { 
    throw new exception(); 
  } 
} 

/// <summary> 
/// c#文件下载 
/// </summary> 
/// <param name="filename"></param> 
public void mydownload(string filename) 
{ 
 
  string path = servermappath("/file/"+filename); 
  if(!fileexists(path)) 
  { 
    responsewrite("对不起！文件不存在！！"); 
    return; 
  } 
  systemiofileinfo file = new systemiofileinfo(path); 
  string filefilt="asp|aspx|php|jsp|ascx|config|asa|"; //不可下载的文件，务必要过滤干净 
  string filename = filename; 
  string fileext = filenamesubstring(filenamelastindexof(""))trim()tolower(); 
  if(filefiltindexof(fileext)!=-1) 
  { 
    responsewrite("对不起！该类文件禁止下载！！"); 
  } 
  else 
  { 
    responseclear(); 
    responseaddheader("content-disposition", "attachment; filename=" + httputilityurlencode(filename)); 
    responseaddheader("content-length", filelengthtostring()); 
    responsecontenttype = getcontenttype(httputilityurlencode(fileext)); 
    responsewritefile(filefullname); 
    responseend(); 
  } 
} 
 
/// <summary> 
/// 获取下载类型 
/// </summary> 
/// <param name="fileext"></param> 
/// <returns></returns> 
public string getcontenttype(string fileext) 
{ 
  string contenttype; 
  switch (fileext) 
  { 
    case "asf": 
      contenttype = "video/x-ms-asf"; break; 
    case "avi": 
      contenttype = "video/avi"; break; 
    case "doc": 
      contenttype = "application/msword"; break; 
    case "zip": 
      contenttype = "application/zip"; break; 
    case "xls": 
      contenttype = "application/vndms-excel"; break; 
    case "gif": 
      contenttype = "image/gif"; break; 
    case "jpg": 
      contenttype = "image/jpeg"; break; 
    case "jpeg": 
      contenttype = "image/jpeg"; break; 
    case "wav": 
      contenttype = "audio/wav"; break; 
    case "mp3": 
      contenttype = "audio/mpeg3"; break; 
    case "mpg": 
      contenttype = "video/mpeg"; break; 
    case "mepg": 
      contenttype = "video/mpeg"; break; 
    case "rtf": 
      contenttype = "application/rtf"; break; 
    case "html": 
      contenttype = "text/html"; break; 
    case "htm": 
      contenttype = "text/html"; break; 
    case "txt": 
      contenttype = "text/plain"; break; 
    default: 
      contenttype = "application/octet-stream"; 
      break; 
  } 
  return contenttype; 
} 

/// <summary> 
/// 获取现有文件的contenttype属性 
/// </summary> 
/// <param name="filename"></param> 
/// <returns></returns> 
public string getfilecontenttype(string filename) 
{ 
  string[] array = filenamesplit(''); 
  string result = stringempty; 
  string suffix = "" + array[arraylength - 1]; 
  microsoftwinregistrykey rg = microsoftwinregistryclassesrootopensubkey(suffix); 
  object obj = rggetvalue("content type"); 
  result = obj != null ? objtostring() : stringempty; 
  rgclose(); 
  return result; 
}