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; 
}