Disabled button doesn't submit postback in Upd

Question

I have a button inside UpdatePanel on my ASP.NET Page. Here's my UpdatePanel

<asp:UpdatePanel ID="UpdateToolbar" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <table>
            <tr>
                <td>
                    <div id="divPDFBtn">
                        <asp:Button ID="btnPrint" runat="server" OnClick="btnPrint_Click" ToolTip="Click to export report to PDF"
                        Width="100px" Text="Print to PDF" OnClientClick="if(PDFClick()) {return true;} else {alert('2');}" />
                    </div>
                </td>
            </tr>
        </table>
    </ContentTemplate>
    <Triggers>
        <asp:PostBackTrigger ControlID="btnPrint" />
    </Triggers>
</asp:UpdatePanel>

When I'm trying to disable button OnClientClick it doesn't do PostBack

Here's example of my PDFClick() function

// Works (does post back and code behind executes))
<script type="text/javascript">
    function PDFClick() {
        document.getElementById("btnPrint").value = "Working...";
        return true;
    };
</script>

// Doesn't work (JS executes, but code behind didn't execute)
<script type="text/javascript">
    function PDFClick() {
        document.getElementById("btnPrint").value = "Working...";
        document.getElementById("btnPrint").disabled = true;
        return true;
    };
</script>

This is my code behind. I need to do some stuff on the back and open new window after it's done:

protected void btnPrint_Click(object sender, EventArgs e)
{
    Response.Write("<script>");
    Response.Write(String.Format("window.open('{0}','_blank')", ResolveUrl("PrintPage.aspx")));
    Response.Write("</script>");
}

Please advise how I can disable my button and reach code behind.

Thanks!

Answer 1

Add ClientIDMode="Static"on the button

<asp:Button ID="btnPrint" runat="server" OnClick="btnPrint_Click" ToolTip="Click to export report to PDF" Width="100px" Text="Print to PDF" OnClientClick="if(PDFClick()) {return true;} else {alert('2');}" ClientIDMode="Static" />

Answer 2

You can disable the button asynchronously with setTimeout:

<script type="text/javascript">
    function PDFClick(btnPrint) {
        btnPrint.value = "Working...";
        setTimeout(function() { btnPrint.disabled = true; }, 10);
        return true;
    };
</script>

The call to document.getElementById can be removed from PDFClick by passing a reference to the button element with the this keyword in OnClientClick:

OnClientClick="if (PDFClick(this)) { return true; } else { alert('2'); }"