圧縮ファイルdoc pdf use 7zipsharp？私のコードが間違っているものを

Question

//この私のコードの圧縮の使用7ジップ

if (System.IO.Directory.Exists(targetfolder)) 
       { 
        try 
        { 

         SevenZipCompressor.SetLibraryPath(@Server.MapPath("~/bin/7z.Libs.16.2.1/bin/x64/7z.dll")); 
         SevenZipCompressor sevenZipCompressor = new SevenZipCompressor(); 
         sevenZipCompressor.CompressionLevel = SevenZip.CompressionLevel.Ultra; // level compress 
         sevenZipCompressor.CompressionMethod = CompressionMethod.Lzma2; //method compress 
         sevenZipCompressor.CompressDirectory(sourceCodeFolder, Path.Combine(targetfolder, string.Concat(DateTime.Now.ToString("ddMMyyyy_HHmm") + fldr + ".zip"))); 
        } 

        catch (Exception se) 
        { 
         SevenZipCompressor.SetLibraryPath(@Server.MapPath("~/bin/7z.Libs.16.2.1/bin/x86/7z.dll")); 
         SevenZipCompressor sevenZipCompressor = new SevenZipCompressor(); 
         sevenZipCompressor.CompressionLevel = SevenZip.CompressionLevel.Ultra; // level compress 
         sevenZipCompressor.CompressionMethod = CompressionMethod.Lzma2; // method compress 

//？ sevenZipCompressor.CompressDirectory（sourceCodeFolder、Path.Combine（targetfolder、string.Concat（DateTime.Now.ToString（ "ddMMyyyy_HHmm"）+ fldr + ".zip"）））;

    } 


        Directory.Delete(@Server.MapPath("~/Upload/" + fldr), true); 
        extractfrom = @Server.MapPath("~/Upload/ZIP/" + string.Concat(DateTime.Now.ToString("ddMMyyyy_HHmm")) + fldr + ".zip"); 

        customSQL.ExecQueryString(" UPDATE TBL_PROGRESS_LEGAL_DOKUMEN set FileName = '" + string.Concat(DateTime.Now.ToString("ddMMyyyy_HHmm") + namafile + ".zip"+ "' , [FileSize] = '" + filesize + "' where id_progress_legal_dokumen = '" + id_chekUpload.Text + "'")); 
        myfeedback._success("File Success Upload"); 
       } 

       else 
       { 

       } 

私の質問なぜ7zipは6MBのみを圧縮するのですか？

Answer 1

（ほとんどの場合）PDFはすでに圧縮されており、アーカイブすることであまり得られません。

Why don't some files compress very much?
Which files does not reduce its size after compression