I'm using Visual Web Developer 2010, this is running on Localhost My autcomplete extender is displaying html page source instead of the database results. I was not able to find the solution pls see my code and help me some one.

 function SetContextKey() {
            $find('AutoCompleteExtender1').set_contextKey($get("<%=ddlstate.ClientID %>").value);
        }

<asp:DropDownList CssClass="select" ID="ddlstate" runat="server">       
                <asp:ListItem Value="Select">Select</asp:ListItem>   
                <asp:ListItem Value="Andhra Pradesh">Andhra Pradesh</asp:ListItem>                                
                <asp:listitem   Value="Andamans">Andamans</asp:listitem>     
                <asp:listitem   Value="Assam">Assam</asp:listitem>
                <asp:listitem   Value="Bihar">Bihar</asp:listitem>
                <asp:listitem   Value="Chhatisgarh">Chhatisgarh</asp:listitem>
                <asp:listitem  value="Delhi">Delhi </asp:listitem>
                <asp:listitem Value="Gujarat">Gujarat</asp:listitem>
                <asp:listitem  value="Haryana">Haryana</asp:listitem>
                <asp:listitem  value ="Himachal Pradesh">Himachal Pradesh</asp:listitem>                
                <asp:listitem  Value="Jammu & Kashmir"> Jammu & Kashmir</asp:listitem>
                <asp:listitem   Value="Jharkhand">Jharkhand</asp:listitem>
                <asp:listitem  Value="Karnataka">Karnataka</asp:listitem>
                <asp:listitem   Value="Kerala">Kerala</asp:listitem>
                <asp:listitem  Value="Maharashtra">Maharashtra</asp:listitem>
                <asp:listitem   Value="Rajasthan">Rajasthan</asp:listitem>
                <asp:listitem   Value="Sikkim">Sikkim</asp:listitem>
                <asp:listitem   Value="Tamil Nadu">Tamil Nadu</asp:listitem>
                <asp:listitem  value ="Telangana">Telangana</asp:listitem>
                <asp:listitem   Value="Uttar Pradesh">Uttar Pradesh</asp:listitem>
                <asp:listitem   Value="Uttaranchal">Uttaranchal</asp:listitem>
                <asp:listitem   Value="West Bengal">West Bengal</asp:listitem>                    
                </asp:DropDownList>
                <asp:RequiredFieldValidator CssClass="validation" ForeColor="#c4e427"
                ID="RequiredFieldValidator5" runat="server"  
                ErrorMessage="Please select your state." ControlToValidate="ddlstate" InitialValue="Select"></asp:RequiredFieldValidator>
                <div class="clr"></div>
                <label class="lable">City</label>
                 <asp:Textbox ID="txtCity" runat="server"  class="inputbox" onkeypress="return noNumeric(event)" onblur="SetContextKey()" ></asp:Textbox>
                <cc1:AutoCompleteExtender ScriptPath="webservice.asmx" ServiceMethod="SearchCustomers"
                MinimumPrefixLength="1"
                CompletionInterval="100" EnableCaching ="false"   CompletionSetCount="10" 
                TargetControlID="txtCity" UseContextKey = "true" FirstRowSelected ="false" 
                ID="AutoCompleteExtender1" runat="server" CompletionListCssClass="AutoExtender"
                CompletionListItemCssClass="AutoExtenderList"
                CompletionListHighlightedItemCssClass="AutoExtenderHighlight"
                CompletionListElementID="divwidth" >
                </cc1:AutoCompleteExtender>
                This is my service code:
public List<string> SearchCustomers(string prefixText, int count, string contextKey)
    {
        try
        { 
            SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["TeN"].ConnectionString);
            using (SqlCommand cmd = new SqlCommand())
            {
                string cmdText = "select cityname from NewCity where " +
                     "StateName like '" + contextKey + "%'";
                //cmd.Parameters.AddWithValue("@SearchText", prefixText);
                if (contextKey != "0")
                {
                    cmdText += " and CityName like  '" + prefixText + "%'";
                    //  cmd.Parameters.AddWithValue("@City", contextKey);
                }
                cmd.CommandText = cmdText;
                cmd.Connection = conn;
                conn.Open();
                List<string> customers = new List<string>();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    while (sdr.Read())
                    {
                        customers.Add(sdr["cityname"].ToString());
                    }
                }
                conn.Close();
                if (customers.Count > 0)
                {
                    return customers;
                }
                else
                {
                    customers.Add("data not found");
                    return customers;

                }

            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }