string zipfile = "c:\\a.zip";
//方法1
FileStream fs = new FileStream(zipfile, FileMode.Open);
//把文件读取到字节数组
byte[] zipdata = new byte[fs.Length];
fs.Read(zipdata, , zipdata.Length);
fs.Close();
//方法2
//把文件读取到字节数组
byte[] zipdata = File.ReadAllBytes(zipfile);