Cannot call modal popup of master page in child page

I am using a modal popup for to display login box. The modal popup is in the master page and associated with a LogIn link therein. Now I want to call the same modal popup in a child page using a different link button. The modal popup can be called by the LogIn link of master page but I want to add this second control (linkButton) in child page, which can call the modalpop of master page.

I tried this in child page:

function LogIn2()
{
$find("programmaticModalPopupBehavior").show();
} 

<asp:LinkButton ID="LinkButton1" runat="server" OnClientClick="LogIn2">Log in</asp:LinkButton>

Reference: multiple TargetControls for the ModalPopup

How to call the functional modal popup of master page from a control in child page??

Update:

This is in masterpage:

<ajax:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="linkLog" CancelControlID="linkClose" BackgroundCssClass="cssM开发者_如何学Pythonodal"                       PopupControlID="panelPopUp" BehaviorID="programmaticModalPopupBehavior" PopupDragHandleControlID="panelDrag"></ajax:ModalPopupExtender>

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Add an OnClientClick for the LinkButton, like this:

<asp:LinkButton ID="LinkButton1" runat="server" Text="Login 2" OnClientClick="return LogIn2()" ...>

Put the JavaScript function in your master page, and after showing the popup, have the method return false to prevent the LinkButton from doing a postback:

function LogIn2()
{
    $find("<%=ModalPopupExtender1.UniqueID%>").show();
    return false;
}

As an alternative, you may also add return false to the OnClientClick of the LinkButton, after the LogIn2 function has executed, like this:

<asp:LinkButton ID="LinkButton1" runat="server" Text="Login 2" OnClientClick="LogIn2();return false;" ...>

---

I m not sure about this but let me confirm are you using the control of ajax like given below

 <asp:ModalPopupExtender ID="ImageUploaderEx" runat="server"  BehaviorID="ImageUploaderBID" TargetControlID="Link Name" CancelControlID="Cancel"  PopupControlID="Panel to be open" OnCancelScript="hideUploader()"></asp:ModalPopupExtender>

If Yes then you can use this same modal with a different name, If this doesnt work let me know I will try my best

try this if it works

((ModalPopupExtender)Page.Master.FindControl("ModalPopupExtender1")).Show();

and add this as well

using AjaxControlToolkit;