Bind data to select option using combogrid jquery-ASP.NET

In my application, when user set cursor or type on select, grid will be appeared beneath select control to show data. and then user will select data. Now, I am using combogrid jquery plugin. I saw a post from other forum like this issue. but I didn't solve.

What I have tried:

in WebService1.asmx, there is a method that return list array.
[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public List AutoArrayList(string Query)
{
//according to the Query parameter to do your logic
List lstStudents = new List();
lstStudents.Add(new Student { StudentID = 1, StudentName = "ABC" });
lstStudents.Add(new Student { StudentID = 2, StudentName = "DEF" });
lstStudents.Add(new Student { StudentID = 3, StudentName = "GHI" });
lstStudents.Add(new Student { StudentID = 4, StudentName = "JKL" });
return lstStudents;
}

public class Student
{
public int StudentID { get; set; }
public string StudentName { get; set; }
}

in Default.aspx,

in body of html

can anyone tell me where the error is and how can I fix this?
Thanks all