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 using System;
using System.Web;
using System.Collections;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Collections.Generic;
using MySql.Data.MySqlClient;


/// <summary>
/// Summary description for acPatientList
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class acPatientList : System.Web.Services.WebService {

    public acPatientList () {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public string[] GetPatientList(string strPrefixText) 
    {
        MySqlConnection cnDBConnection = new MySqlConnection();
        MySqlCommand cmPatientList = new MySqlCommand();
        MySqlDataReader rdPatientList;

        List <string> result = new List<string>();
        
        cnDBConnection.ConnectionString = clsFunction.strConnection;
        cnDBConnection.Open();
        cmPatientList.Connection = cnDBConnection;
        cmPatientList.CommandText = "SELECT patientid, CONCAT(lname,', ',fname,' ',mname) AS patient " +
                                    "FROM patientlist WHERE lname LIKE '" + clsFunction.ReplaceString(strPrefixText) + 
                                    "%'";
        rdPatientList = cmPatientList.ExecuteReader();
        
        while(rdPatientList.Read())
        {
            result.Add(rdPatientList[0].ToString() + "-" + rdPatientList[1].ToString());
        }
        rdPatientList.Close();
        cmPatientList.Connection.Close();
        cnDBConnection.Close();
        return result.ToArray();


    }
    
}

 <asp:ScriptManager ID="ScriptManager" runat="server">
                    <Services>
                        <asp:ServiceReference Path="acPatientList.asmx" />
                    </Services>
                </asp:ScriptManager>
                <cc1:AutoCompleteExtender ID="AutoCompleteExtender" runat="server" ServiceMethod="GetPatientList"
                    ServicePath="acPatientList.asmx" MinimumPrefixLength="1" TargetControlID="txtPatientName" CompletionSetCount="10" EnableCaching="true">
                </cc1:AutoCompleteExtender>
                <asp:Label ID="Label1" runat="server" Text="Request ID:" Width="87px"></asp:Label><asp:TextBox
                    ID="txtRequestID" runat="server" BackColor="White" Font-Bold="True" ReadOnly="True"></asp:TextBox>
                <br />
                <asp:Label ID="Label3" runat="server" Text="Patient Name:" Width="87px"></asp:Label><asp:TextBox
                    ID="txtPatientName" runat="server" Width="303px" BackColor="White"></asp:TextBox><br />
                <asp:Label ID="Label4" runat="server" Text="Requested By:" Width="87px"></asp:Label><asp:TextBox
                    ID="txtRequestedBy" runat="server" Width="303px" BackColor="White"></asp:TextBox>&nbsp;</div>