ASP.Net SQLDataSource Session Parameter not filterting data in DataList

I have a catalog function whereby user can filter their selection by clicking radiobutton. For example, by selecting the Dining radiobutton, all packages related to dining would appear.

And i using DataList1.Items.Count method to count the number search result. I had implement this method in the page_load, however the value of the number of datalist keep displaying previously loaded datalist.

Here is my code :

 protected void Page_Load(object sender, EventArgs e)
    {  
        DataList1.DataSourceID = "SqlDataSource3";
        Label1.Text = DataList1.Items.Count.ToString(); 
    }


    private SqlDataReader getReader()
    {
        //get connection string from web.config
        string strConnectionString = ConfigurationManager.ConnectionStrings["ASPNETDBConnectionString1"].ConnectionString;
        SqlConnection myConnect = new SqlConnection(strConnectionString);

        string strCommandText = "SELECT CategoryID, CatName  from Category";

        SqlCommand cmd = new SqlCommand(strCommandText, myConnect);
        myConnect.Open();

        //DataList1.DataSource = reader; 

        DataList1.DataBind();

        // CommandBehavior.CloseConnection will automatically close connection
        SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        return reader;
    }

    protected void RadioButtonList1_SelectedIndexChanged(object sender, EventArgs e)
    { 
        DataList1.DataSourceID = "SqlDataSource1";


        if (RadioButtonList1.SelectedIndex == 0)
        {
            Session["catID"] = 1;

        }
        else if (RadioButtonList1.SelectedIndex == 1)
        {
            Session["catID"] = 2;

        }
        else if (RadioButtonList1.SelectedIndex == 2)
        {
            Session["catID"] = 3; 

        }
        else if (RadioButtonList1.SelectedIndex == 3)
        {
            Session["catID"] = 4;

        }
        else if (RadioButtonList1.SelectedIndex == 4)
        {
            Session["catID"] = 5;

        }

        else
        {
            Session["catID"] = 8;

        }

    } 

I had tried to place the Item.Count in other places of this code, but same problem persist..

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
        ConnectionString="<%$ ConnectionStrings:ASPNETDBConnectionString1 %>"
                
        SelectCommand="SELECT [CategoryID], [AnniID], [Title], [Price], [Image1] FROM [Anniversary]  WHERE ([CategoryID] = @CategoryID) ">
            <SelectParameters>
            <asp:SessionParameter Name="CategoryID" SessionField="catID" Type="Int32" />
        </SelectParameters>
         
        </asp:SqlDataSource>
 
        <asp:SqlDataSource ID="SqlDataSource2" runat="server"
        ConnectionString="<%$ ConnectionStrings:ASPNETDBConnectionString1 %>"
        SelectCommand="SELECT * FROM [Category]"></asp:SqlDataSource>
 
    <asp:SqlDataSource ID="SqlDataSource3" runat="server"
        ConnectionString="<%$ ConnectionStrings:ASPNETDBConnectionString1 %>"
         
        SelectCommand="SELECT [Title], [Description], [Image1], [Price], [StartDate], [EndDate], [AnniID] FROM [Anniversary]">
    </asp:SqlDataSource>
 
    <asp:RadioButtonList ID="RadioButtonList1" runat="server"
        RepeatDirection="Horizontal" AutoPostBack="True" DataTextField="CatName"
        DataValueField="CategoryID" DataSourceID="SqlDataSource2"
        onselectedindexchanged="RadioButtonList1_SelectedIndexChanged" >
    </asp:RadioButtonList> 
 
    <br /> <br />   
 
    <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label> 
 
 
    <asp:DataList ID="DataList1" DataKeyField="AnniID" runat="server" DataSourceID="SqlDataSource1" RepeatColumns="3" >
        <ItemTemplate>
           
 
           <%--   <asp:Label ID="TitleLabel" runat="server" Text='<%# Eval("Title") %>' />--%>
           <a href='AnniProdDetails.aspx?AnniID=<%# Eval("AnniID") %>'><%# Eval("Title") %><br></a>
 
            <asp:Label ID="PriceLabel" runat="server" Text='<%# Eval("Price") %>' />
               <br />
   <asp:Image ID="Image1" runat="server"
         ImageUrl='<%# Eval("Image1", "~/Images/{0}") %>'  Height="150" Width="200" />
            <br />
            <br />
        </ItemTemplate>
    </asp:DataList>