Compress File

byte[] bufferWrite;
FileStream fsSource, fsDest;
GZipStream zip;
fsSource = new FileStream(Server.MapPath("") + "/wr.xls", FileMode.Open, FileAccess.Read, FileShare.Read);
bufferWrite = new byte[fsSource.Length];
fsSource.Read(bufferWrite, 0, bufferWrite.Length);

fsDest = new FileStream(Server.MapPath("") + "\\MyCompressFile.rar", FileMode.OpenOrCreate, FileAccess.Write);

zip = new GZipStream(fsDest, CompressionMode.Compress, true);

zip.Write(bufferWrite, 0, bufferWrite.Length);


fsSource.Close();
zip.Close();
fsDest.Close();