Guys please help me!!how to download xml file from url in android device runtime

Basically i want to read data from url and store it to xml file during runtime in android device.So that i can use the xml file in further reference in my android apk

And one more doubt -how to convert string to text asset

Below is a small trail that i did for xml download,but of no use

public class XmlTest : MonoBehaviour {
        public  XmlDocument DataFrmOnline;
         string url;
        public string[] str;
        public string str1;
         public TextAsset xmltextasset;
    // Use this for initialization
        void Start () {
     // Update is called once per frame
        void Update () {
        IEnumerator IsFinishDownload (string url) {
             WWW hs_get = new WWW(url);
              yield return hs_get;
             str1= hs_get.text;
              DataFrmOnline = loadxmldocu(hs_get.text);  //this works good if i input       textasset instead of www.text
        public static XmlDocument loadxmldocu(TextAsset xmlfile)
            MemoryStream assetstream = new MemoryStream (xmlfile.bytes);
            XmlReader reader = XmlReader.Create(assetstream);
            XmlDocument xmlDoc = new XmlDocument();
            return xmlDoc;

public Texture2D TextureContainer;
void Start()
IEnumerator FinishDownload_Image (string url,Texture2D TexturToCopy, int no) {
WWW hs_get2 = new WWW(url);

		yield return hs_get2;
		//sun= hs_get.texture;
		//print("image url finsh__"+url);
		TexturToCopy= hs_get2.texture;//TexturToCopy-consists of image that resides in the url