How to get JSON string from Android?

How to get JSON string from Android?

I made web service server application with .Net and this is my JSON output
<?xml version="1.0" encoding="utf-8"?>
<string xmlns="http://stockcluster.com/">
{
"percentageArray":[85.0,13.0,2.0]
}
</string>
I want to know how to get this string from android. I tried myself but
"cannot convert to JSONObject from string" error occured.
My code is here:
double[] percentageArray = new double[3] {
lowPersentage,
normalPersentage,
highPersentage
};
json = JsonConvert.SerializeObject(new { percentageArray });
return json;
please help me !