Cannot get value of UpdatePanel element

I have a repeater inside an Update Panel. when I click the "Find Books" button repeater is modified according to the query.

What I want is to get the value of the DropDown when I click Add To Cart Button. But I can't get the value, instead the UpdatePanelAnimationExtender runs again. I added another button (TestingButton) inside the Update Panel. The UpdatePanelAnimationExtender runs when I click that button also.

My question is how can restrict the update panel only to the "Find Books" button? and how can I retrieve the value of DropDown outside the update panel? I added UpdateMode to conditional but it also not working.

aspx page

        <p>Search by Author</p>
    <asp:TextBox ID="txtAuthor" runat="server" Text="" AutoComplete="off" /><br />
    <p>Search by Publisher</p>
    <asp:TextBox ID="txtPublisher" runat="server" Text="" AutoComplete="off" /><br />
    <asp:Button ID="btnFind" runat="server" Text="Find Books" OnClick="BtnFind_Click" />
    <br />
    <p>Search by Price</p>
    <asp:RadioButtonList ID="RadioButtonList1" runat="server">
        <asp:ListItem Text="Below Rs. 1000.00"></asp:ListItem>
        <asp:ListItem Text="Between Rs. 1001 to 2500"></asp:ListItem>
        <asp:ListItem Text="Above Rs. 2501.00"></asp:ListItem>
    </asp:RadioButtonList>
    <br />
    <asp:TextBox ID="txtTest" runat="server"></asp:TextBox>
            <asp:Button ID="Button2" runat="server" Text="Button" 
        onclick="Button1_Click" />


    <asp:UpdatePanel ID="udpBooks" UpdateMode="Conditional"  runat="server">
        <ContentTemplate>
            <asp:Button ID="btnTest" runat="server" Text="Testing Button" onclick="Button1_Click" />
            <asp:Repeater ID="repBooks" runat="server" DataSourceID="SqlDataSource1" 
                onitemcommand="repBooks_ItemCommand">
                <HeaderTemplate>
                </HeaderTemplate>
                <ItemTemplate>
                    <div id="bookBorder">
                        <table width="640px" height="70px" border="0">
                            <tr>
                                <td width="51%" style="padding-top: -20px">
                                    <span class=开发者_高级运维"title">Description:</span> :
                                    <%# DataBinder.Eval(Container.DataItem, "description")%>
                                </td>
                                <td>
                                    <asp:DropDownList ID="DropDownList2" CssClass="dropDown" runat="server" Width="100px">
                                        <asp:ListItem>1</asp:ListItem>
                                        <asp:ListItem>2</asp:ListItem>
                                        <asp:ListItem>3</asp:ListItem>
                                    </asp:DropDownList>
                                    <br />
                                    <asp:Button ID="btnAddToCart" CssClass="button" runat="server" Text="Add to Cart"
                                        OnClick="BtnAddToCart_Click" />
                                </td>
                            </tr>
                        </table>
                    </div>
                    <br />
                </ItemTemplate>
            </asp:Repeater>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="btnFind" EventName="Click" />
        </Triggers>
    </asp:UpdatePanel>
    <asp:UpdatePanelAnimationExtender ID="upae1" runat="server" TargetControlID="udpBooks">
        <Animations>
                 <OnUpdating>
                    <Parallel Duration="0">
                        <EnableAction AnimationTarget="btnFind" Enabled="false" />
                        <FadeOut MinimumOpacity=".5" />
                    </Parallel>
                </OnUpdating>
                <OnUpdated>
                    <Parallel Duration="0">
                        <FadeIn MinimumOpacity=".8" />
                        <EnableAction AnimationTarget="btnFind" Enabled="true" />
                    </Parallel>                    
                </OnUpdated>
        </Animations>
    </asp:UpdatePanelAnimationExtender>

Code Behind

    public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void SqldsOrderDetails_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {
        string author = txtAuthor.Text;
        string publisher = txtPublisher.Text;
        string select = "";


        if (author.Equals("") && publisher.Equals(""))
            select = "select bookId, ISBN, Title, publisher, author, price, description from dbo.[book]";
        else if(author.Equals("") && !publisher.Equals(""))
            select = "select bookId, ISBN, Title, publisher, author, price, description from dbo.[book] where publisher=@publisher ";
        else if(!author.Equals("") && publisher.Equals(""))
            select = "select bookId, ISBN, Title, publisher, author, price, description from dbo.[book] where author=@author";
        else if(!author.Equals("") && !publisher.Equals(""))
            select = "select bookId, ISBN, Title, publisher, author, price, description from dbo.[book] where author=@author and publisher=@publisher";

        SqlDataSource1.SelectCommand = select;
        e.Command.Parameters.Add(new SqlParameter("@author", this.txtAuthor.Text));
        e.Command.Parameters.Add(new SqlParameter("@publisher", this.txtPublisher.Text));
    }
    protected void BtnFind_Click(object sender, EventArgs e)
    {
        System.Threading.Thread.Sleep(2000);
//        this.gvOrderDetails.DataBind();
        this.repBooks.DataBind();
    }
    protected void ul_Click(object sender, EventArgs e)
    {
        Response.Redirect("default.aspx");
    }

    protected void BtnAddToCart_Click(object sender, EventArgs e)
    {
        txtTest.Text = "sd";
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        txtTest.Text = "sd";
    }
    protected void repBooks_ItemCommand(object source, RepeaterCommandEventArgs e)
    {
        DropDownList d = e.Item.FindControl("DropDownList2") as DropDownList;
        txtTest.Text = d.SelectedValue;
        Button b= e.Item.FindControl("btnAddToCart") as Button;
        b.Text = d.SelectedValue;
    }
}

For triggering

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        Some content that needs to be updated here...
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="FindBook" EventName="Click" />
    </Triggers>
</asp:UpdatePanel>

as far as the value of DropDown into textbox is concern, you should place textbox in another updatepanel and set its value when user select a value from dropdown by calling update method.