利用Win32API 读取文件头获取Mime-Type

第一个种方式利用Win32API 读取文件头获取Mime-Type

  

    [DllImport(
   @"
   urlmon.dll
   "
   , CharSet 
   =
    CharSet.Auto)] 
 
   private
    
   extern
    
   static
    System.UInt32 FindMimeFromData( 
 System.UInt32 pBC, 
 [MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl, 
 [MarshalAs(UnmanagedType.LPArray)] 
   byte
   [] pBuffer, 
 System.UInt32 cbSize, 
 [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed, 
 System.UInt32 dwMimeFlags, 
 
   out
    System.UInt32 ppwzMimeOut, 
 System.UInt32 dwReserverd 
 );

 
   public
    
   string
    getMimeFromFile(
   string
    filename) 
 { 
 
   if
    (
   !
   File.Exists(filename)) 
 
   throw
    
   new
    FileNotFoundException(filename 
   +
    
   "
    not found
   "
   );

 
   byte
   [] buffer 
   =
    
   new
    
   byte
   [
   256
   ]; 
 
   using
    (FileStream fs 
   =
    
   new
    FileStream(filename, FileMode.Open)) 
 { 
 
   if
    (fs.Length 
   >=
    
   256
   ) 
 fs.Read(buffer, 
   0
   , 
   256
   ); 
 
   else
    
 fs.Read(buffer, 
   0
   , (
   int
   )fs.Length); 
 } 
 
   try
    
 { 
 System.UInt32 mimetype; 
 FindMimeFromData(
   0
   , 
   null
   , buffer, 
   256
   , 
   null
   , 
   0
   , 
   out
    mimetype, 
   0
   ); 
 System.IntPtr mimeTypePtr 
   =
    
   new
    IntPtr(mimetype); 
 
   string
    mime 
   =
    Marshal.PtrToStringUni(mimeTypePtr); 
 Marshal.FreeCoTaskMem(mimeTypePtr); 
 
   return
    mime; 
 } 
 
   catch
    (Exception e) 
 { 
 
   return
    
   "
   unknown/unknown
   "
   ; 
 } 
 }

 
  

第二种方式 利用系统注册表查找Mime-Type

  

   using
    System.IO;
 
   using
    Microsoft.Win32;

 
   string
    GetMimeType(FileInfo fileInfo)
 {
 
   string
    mimeType 
   =
    
   "
   application/unknown
   "
   ;

 RegistryKey regKey 
   =
    Registry.ClassesRoot.OpenSubKey(
 fileInfo.Extension.ToLower()
 );

 
   if
   (regKey 
   !=
    
   null
   )
 {
 
   object
    contentType 
   =
    regKey.GetValue(
   "
   Content Type
   "
   );

 
   if
   (contentType 
   !=
    
   null
   )
 mimeType 
   =
    contentType.ToString();
 }

 
   return
    mimeType;
 }