[WebMethod]
public byte[] GetNewVersion(string version)
{


    string filename = @"~/dir/AppFile.apk";
    BinaryReader binReader = new
    BinaryReader(File.Open(Server.MapPath(filename), FileMode.Open,FileAccess.Read));
    binReader.BaseStream.Position = 0;
    byte[] binFile =
    binReader.ReadBytes(Convert.ToInt32(binReader.BaseStream.Length));
    binReader.Close();
    return binFile;
}

[WebMethod]
public void PutFile(byte[] buffer, string filename)
{
    BinaryWriter binWriter = new
    BinaryWriter(File.Open(Server.MapPath(filename), FileMode.CreateNew, FileAccess.ReadWrite));
    binWriter.Write(buffer);
    binWriter.Close();
}

response = envelope.getResponse();
byte[] b = response.toString().getBytes();
filePath = Environment.getExternalStorageDirectory().getPath() + "/download/" + "VersionUpdatee" + ".apk";

File file = new File(filePath);

//If already file there so delete it.
if (file.exists())
file.delete();

    file.getParentFile().mkdirs();
    file.createNewFile();

    BufferedOutputStream objectOut = new BufferedOutputStream(new FileOutputStream(file));
     objectOut.write(b);
     objectOut.close();

filePath = Environment.getExternalStorageDirectory().getPath() + "/download/" + "VersionUpdatee" + ".apk";
String command = "chmod " + "666" + " " + filePath;
Runtime runtime = Runtime.getRuntime();
 try {
runtime.exec(command);
} catch (IOException e) {

e.printStackTrace();
}

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(new File(filePath)), "application/vnd.android.package-archive");
startActivity(intent);