string zipFileName = Server.MapPath("/sample.zip");
string sourceFile = Server.MapPath("/code.txt");
string zipname = "zip\\code.txt";
java.io.FileOutputStream fos = new java.io.FileOutputStream(zipFileName);

// Tie to zip stream 
java.util.zip.ZipOutputStream zos = new java.util.zip.ZipOutputStream(fos);

// Stream with source file 
java.io.FileInputStream fis = new java.io.FileInputStream(sourceFile);

// It's our entry in zip 
java.util.zip.ZipEntry ze = new java.util.zip.ZipEntry(zipname);

zos.putNextEntry(ze);
sbyte[] buffer = new sbyte[1024];
int len;

// Read and write until done 
while ((len = fis.read(buffer)) >= 0)
{
    zos.write(buffer, 0, len);
}

// Close everything 
zos.closeEntry();
fis.close();
zos.close();