C＃只读取第一行，使用压缩文本文件的StreamReader

Question

I am trying to read only the first line of a zipped csv file. I used below code but get the error "The magic number in GZIP header is not correct". Obviously it has to do with the fact that GZIP and ZIP are not identical formats but I do not seem to get it working even when using the DotNetZipLib library or SharpZip.

using (GZipStream gzipStream = new GZipStream(File.OpenRead(fileName), CompressionMode.Decompress))
            {
                using(StreamReader sr = new StreamReader(gzipStream))
                {
                    //Matt try something like this as a hint / starting point 
                    While(sr.Read())
                    {
                      row = sr.ReadLine();
                    }

                }
            }

Does any of you know how to handle standard zip files (not gzip) and to stream the content to a StreamReader object so that I can easily read the first line of the zipped text file? I do not look for a solution that completely decompresses the whole zip file before opening the text file. I look for a similar solution as above but one that can handle zip files. I also do not want to go the geeky route through byte arrays and having to reconstruct the first row from the array as it would require knowledge of the exact content of the first row (data types, delimiters,...).

Thanks

Answer 1

for example Matt here is something that you could do as well checkout this code sample This uses SharpZipLib Library

var zip = new ZipInputStream(File.OpenRead(@"C:\MyZips\myzip.zip"));
var filestream = new FileStream(@"C:\\MyZips\myzip.zip", FileMode.Open, FileAccess.Read);
ZipFile zipfile = new ZipFile(filestream);
ZipEntry item;
while ((item = zip.GetNextEntry()) != null)
{
     Console.WriteLine(item.Name);
     using (StreamReader s = new StreamReader(zipfile.GetInputStream(item)))
     {
      // stream with the file
          Console.WriteLine(s.ReadToEnd());
     }
 }

Answer 2

The above answer didnt work for me (it casted an error at runtime: nullreference for "item") so i modified the code a bit.(a text file called "text.txt" is zipped in a zip called "archive.zip") This one is in VB.NET and uses SHARPZIPLIB library(you must import it into VB and call it before public class mainform.

here is the code :

       Imports ICSharpCode.SharpZipLib.Zip

'now put the following code in a private sub ( i put it in private sub button_click)

       Dim zip As New ZipInputStream(File.OpenRead("c:\archive.zip")) 'location of the zip file
       Dim filestream As New FileStream("c:\archive.zip", FileMode.Open,FileAccess.Read)
        Dim zipfile As ZipFile = New ZipFile(filestream)

        Dim item As ICSharpCode.SharpZipLib.Zip.ZipEntry
        item = New ZipEntry("text.txt")

        While (Not (zip.GetNextEntry) Is Nothing)
            Console.WriteLine(item.Name)
            Dim s As StreamReader = New StreamReader(zipfile.GetInputStream(item))
            ' stream with the file
            MsgBox(s.Readline)

        End While
        end sub

When u run the code, The message box will popup with the text that is entered in the first line of a text file text.txt Hope this helps. Cheers!