json string deserialization

private void button17_Click(object sender, EventArgs e)
{
string s = "{\"returnCode\":0,\"returnMessage\":\"\u6210\u529f\",\"returnData\":{\"expect\":\"20190716058\",\"opencode\":\"10,8,7,5,9,3,4,1,2,6\"}}";
returnData data = JsonConvert.DeserializeObject<returnData>(s);
var sd = JObject.Parse(s)["returnData"];
returnData returnData = JsonConvert.DeserializeObject<returnData>(JObject.Parse(s)["returnData"].ToString());
}