Download 1 file Parse Unity

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Parse;

public class ParseManager : MonoBehaviour {

    void Start () {
        Download();
    }

    public void Download(){
        string id_facebook = "idfbtest";
        string filename = "hinhanh.png";
        StartCoroutine(LoadFile(id_facebook, filename));
    }

    IEnumerator LoadFile(string id_facebook, string filename)   //single method downloads file
    {
        ParseQuery<ParseObject> query = ParseObject.GetQuery("Sync").WhereEqualTo("id_facebook", id_facebook);

        var queryTask = query.FirstAsync();
        while (!queryTask.IsCompleted) yield return null;

        ParseObject obj = queryTask.Result;

        ParseFile pfile = obj.Get<ParseFile>("file_datauser");
        int level = obj.Get<int>("level");
        print ("level " + level);
        Debug.Log(pfile.Url.AbsoluteUri);
        WWW www = new WWW(pfile.Url.AbsoluteUri);
        yield return www;
        //Debug.Log("imageRequest " + imageRequest.text);
        byte[] bytes = www.bytes;
        String urlFile = Application.persistentDataPath + "/" + "ten" + level + ".png";//filename;
        print ("duong dan: " + urlFile);
        System.IO.File.WriteAllBytes(urlFile, bytes);

    }

}