c# - Remove last x lines from a streamreader -

i need read in last x lines file streamreader in c#. best way this?

many thanks!

if it's large file, possible seek end of file, , examine bytes in reverse '\n' character? aware \n , \r\n exists. whipped following code , tested on trivial file. can try testing on files have? know solution looks long, think you'll find it's faster reading beginning , rewriting whole file.

public static void truncate(string file, int lines) {     using (filestream fs = file.open(file, filemode.openorcreate, fileaccess.readwrite, fileshare.none))     {         fs.position = fs.length;          // \n \r\n (both uses \n lines)         const int buffer_size = 2048;          // start @ end until # lines have been encountered, record position, truncate file         long currentposition = fs.position;         int linesprocessed = 0;          byte[] buffer = new byte[buffer_size];         while (linesprocessed < linestotruncate && currentposition > 0)         {             int bytesread = fillbuffer(buffer, fs);              // have buffer containing later contents of file             (int = bytesread - 1; >= 0; i--)             {                  currentposition--;                  if (buffer[i] == '\n')                  {                      linesprocessed++;                      if (linesprocessed == linestotruncate)                          break;                  }             }         }          // truncate file         fs.setlength(currentposition);     } }  private static int fillbuffer(byte[] buffer, filestream fs) {     if (fs.position == 0)         return 0;      int bytesread = 0;     int currentbyteoffset = 0;      // calculate how many bytes of buffer can filled (remember we're going in reverse)     long expectedbytestoread = (fs.position < buffer.length) ? fs.position : buffer.length;     fs.position -= expectedbytestoread;      while (bytesread < expectedbytestoread)     {         bytesread += fs.read(buffer, currentbyteoffset, buffer.length - bytesread);         currentbyteoffset += bytesread;     }      // have reset position again because moved reader forward;     fs.position -= bytesread;     return bytesread; } 

since planning on deleting end of file, seems wasteful rewrite everything, if it's large file , small n. of course, 1 can make argument if wanted eliminate lines, going beginning end more efficient.