Hi  micah,
Refer below sample.
HTML
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $.ajax({
            type: "POST",
            url: "CS.aspx/GetData",
            data: '{}',
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (response) {
                var xmlDoc = $.parseXML(response.d);
                var xml = $(xmlDoc);
                var customers = xml.find("Table");
                var rows = '';
                $.each(customers, function () {
                    var id = $(this).find("CustomerId").text();
                    var name = $(this).find("Name").text();
                    var country = $(this).find("Country").text();
                    rows += "<tr><td>" + id + "</td><td>" + name + ' ' + "</td><td>" + country + "</td></tr>";
                });
                $('.tblCustomers tbody').append(rows);
            },
            error: function (response) {
                var r = jQuery.parseJSON(response.responseText);
                alert("Message: " + r.Message);
            }
        });
    });
</script>
<div>
    <table class="tblCustomers" border="1">
        <thead>
            <tr>
                <th>Id</th>
                <th>Name</th>
                <th>Contry</th>
            </tr>
        </thead>
        <tbody>
        </tbody>
    </table>
</div>
Namespaces
C#
using System.Data.SqlClient;
using System.Configuration;
using System.Data;
using System.Web.Services;
VB.Net
Imports System.Data.SqlClient
Imports System.Web.Services
Imports System.Data
Code
C#
[WebMethod]
public static string GetData()
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ToString()))
    {
        SqlCommand cmd = new SqlCommand("SELECT CustomerId,Name,Country FROM CustomerTest");
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataSet ds = new DataSet())
            {
                sda.Fill(ds);
                return ds.GetXml();
            }
        }
    }
}
VB.Net
<WebMethod()>
Public Shared Function GetData() As String
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ToString())
        Dim cmd As SqlCommand = New SqlCommand("SELECT CustomerId,Name,Country FROM CustomerTest")
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using ds As DataSet = New DataSet()
                sda.Fill(ds)
                Return ds.GetXml()
            End Using
        End Using
    End Using
End Function
Screenshot
