asp.net ajax not working, page still refreshes

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ASP.NET

Ajax

UpdatePanel

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hey all,
long story short:
I have a few links that represent project categories. on each of the links click, a datagrid on the same page gets populated with appropriate data. I wanna use ajax functionality, I use .net framework 4.5 with entity framework 5. I placed the links and gridview both in the same update panel but the page still refreshes when i click on any of the links.
Please let me know if you want me to paste any code parts to aid you in pointing the problem.
Many thanks in advance :)

ASPX CODE:

<asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"></asp:ToolkitScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Always" ChildrenAsTriggers="true" runat="server">
            <ContentTemplate>
                <div>
        <asp:DropDownList ID="DropDownList1" runat="server" ></asp:DropDownList>
        <asp:TextBox ID="TextBox1" runat="server" TextMode="Date" />
    </div>
                <asp:Repeater runat="server" ID="rptProjectStates">
                    <HeaderTemplate>
                        <ul>
                    </HeaderTemplate>
                    <ItemTemplate>
                        <li>
                            <asp:LinkButton ID="lbProjectStatus" Text='<%#Eval("ProjectStatusTypeName") %>' 

OnClick="lbProjectStatus_Click" runat="server" /></li>
                    </ItemTemplate>
                    <FooterTemplate>
                        </ul>
                    </FooterTemplate>
                </asp:Repeater>
                <asp:GridView runat="server" ID="gvProjects">
                    <Columns>
                        <asp:TemplateField>
                            <HeaderTemplate>
                                <asp:Label Text="Project No" runat="server" />
                                <br />
                                <asp:TextBox runat="server" ID="txtFilterProjID" OnTextChanged="txtFilterProjID_TextChanged" AutoPostBack="true" />
                            </HeaderTemplate>
                            <ItemTemplate>
                                <asp:Label Text='<%#Eval("Title") %>' runat="server" />
                            </ItemTemplate>
                        </asp:TemplateField>
                    </Columns>
                </asp:GridView>
            </ContentTemplate>
        </asp:UpdatePanel>

BACK END CODE:

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using SafatES.SPIS.DAL.ProjectServer;
using System.Configuration;
using SPIS.DATA;

namespace SPIS_Remake
{
    public partial class PSTest : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            PopulateStatusTypes();

            using (SPISDBOnlineEntities dc = new SPISDBOnlineEntities())
            {
                rptProjectStates.DataSource = dc.ProjectStatusTypes.ToList();
                rptProjectStates.DataBind();
            }
        }

        private void PopulateStatusTypes()
        {
            Uri pwaUri = new Uri("http://projects.safates.com:80/");
            SafatES.SPIS.DAL.ProjectServer.Project projects= new SafatES.SPIS.DAL.ProjectServer.Project(pwaUri, ConfigurationSettings.AppSettings["PSIUsername"].ToString(), ConfigurationSettings.AppSettings["PSIPassword"].ToString(), ConfigurationSettings.AppSettings["PSIDomain"].ToString());

            /* Populate Branches */
            DataTable dtProjectStatus = Helpers.DynamicGetLookUpTable("SafatES-Clients");
            DropDownList1.DataSource = dtProjectStatus;
            DropDownList1.DataValueField = "LT_STRUCT_UID";
            DropDownList1.DataTextField = "LT_VALUE_TEXT";
            DropDownList1.DataBind();

            SafatES.SPIS.DAL.ProjectServer.Helpers.DisposeClients();
        }

        protected void txtFilterProjID_TextChanged(object sender, EventArgs e)
        {

        }

        protected void lbProjectStatus_Click(object sender, EventArgs e)
        {
            LinkButton lb = (LinkButton)sender;
            using (var dc = new SPISDBOnlineEntities())
            {
                gvProjects.DataSource = (from projs in dc.ViewProjects
                                         where projs.ProjectStatusTypeName == lb.Text
                                         select projs).ToList();
                gvProjects.DataBind();
            }
        }

        
    }
}