jquery dialog is not rendering partial view

Hi all,
Iam trying to render a partial view inside of jquery dialog, but every time it is throwing me empty dialog box with nothing in it.

Here is the code for it can any one please take a look into it. thanks
Action method

public ActionResult UpdateUser(string Userid) {
HttpClient client = new HttpClient(); client.BaseAddress = new Uri(ApiUrlBaseAddress);
List<SelectedUserItem> Users = new List<SelectedUserItem>();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response;
response = client.GetAsync("api/UserMaintenance" + "/" +Userid).Result;
if (response.IsSuccessStatusCode) { string result = response.Content.ReadAsStringAsync().Result;
JavaScriptSerializer serializer = new JavaScriptSerializer();
dynamic returnedata = serializer ...