How to access the TextArea value from a content pa

I have a TextArea control in my content page which is inside an UpdatePanel:

<asp:UpdatePanel runat="server" ClientIDMode="Static" ID="upTaskDetailRight" UpdateMode="Conditional">
    <ContentTemplate>
        <div style="width: 98%; padding-bottom: 10px;" class="brClear">
            <div style="width: 98%; height: 120px;">
                <textarea id="taskNotes" runat="server" class="taskNotes" style="width: 100%; height: 100%; scrollbar-base-color: #A0A0A0; scrollbar-base-color: #A0A0A0; scrollbar-3dlight-color: #A0A0A0; scrollbar-highlight-color: #A0A0A0; scrollbar-track-color: #EBEBEB; scrollbar-arrow-color: #FFFFFF; scrollbar-shadow-color: #A0A0A0; scrollbar-darkshadow-color: #A0A0A0;"></textarea>
            </div>
        </div>
    </ContentTemplate>
</asp:UpdatePanel>

I have a button in my MasterPage which is accessing the TextArea value from the content page and updating the SQL Database:

<asp:Panel ID="Panel93" runat="server" CssClass="navInnerDivContentsTopSubTwo">
    <asp:ImageButton ID="ibSave" ImageUrl="~/theImages/Save.png" runat="server" CssClass="navImages" OnClick="btnSave_Click" />
    <br />
    <asp:LinkButton ID="btnSave" runat="server" Text="Save" ClientIDMode="Static" OnClick="btnSave_Click" CssClass="linkOff" />
</asp:Panel>

Code-behind:

System.Web.UI.HtmlControls.HtmlTextArea lblTDNotes;
lblTDNotes = (System.Web.UI.HtmlControls.HtmlTextArea)ContentMain.FindControl("taskNotes");
protected void btnSave_Click(object sender, EventArgs e)
{
    string strSaveQuery = @"UPDATE HSI.RMMEMO SET MEMO = '" + lblTDNotes.Value + "' WHERE MEMOID = '" + hfMemoIDYT.Value  + "'";
    //MessageBox.Show(strSaveQuery);

    using (SqlConnection scConn = new SqlConnection(strMainConn))
    {
        try
        {
            scConn.Open();
            SqlCommand cmd = new SqlCommand(strSaveQuery, scConn);

            cmd.ExecuteNonQuery();

            Response.Redirect("YourTasks.aspx");
        }
        catch (Exception ce)
        {
        }
    }
}

When the page loads, the TextArea has some pre populated data. If I make any changes to the TextArea data (add or remove text) and hit the SAVE button in the Master page, the lblTDNoted.Value from the strSaveQuery is using the pre populated data and not the updated entry.

How do I get the updated entry from the textarea?

Add <triggers> to your UpdatePanel.

<asp:UpdatePanel runat="server" ...>
    <ContentTemplate>
        ...
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="btnSave" EventName="Click" />
    </Triggers>
</asp:UpdatePanel>