how do I access user control method in aspx page

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ASP.NET

C#5.0

I have user control with modal popup which is used to show popup whenever necessary.

<div class="modal fade" id="myModal" role="dialog" aria-labelledby="myModalLabel"
    aria-hidden="true">
    <div class="modal-dialog modal-sm">
         <asp:UpdatePanel ID="upModal" runat="server" ChildrenAsTriggers="false" UpdateMode="Conditional">
            <ContentTemplate>
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">
                    ×</button>
                <h4 class="modal-title">
                    <asp:Label ID="lblModalTitle" runat="server"></asp:Label></h4>
            </div>
            <div class="modal-body">
                <asp:Label ID="lblModalBody" runat="server"></asp:Label>
            </div>
            <div class="modal-footer">
                <button class="btn btn-info" data-dismiss="modal" aria-hidden="true">
                    Close</button>
            </div>
        </div>
        </ContentTemplate>
        </asp:UpdatePanel>
    </div>
</div>

And back end

private string _Title = null;

public string Title
        {
        get
            {
            return _Title;
            }
        set
            {
            _Title = value;
            }
        }

private string _message = null;

public string Message
        {
        get
            {
            return _message;
            }
        set
            {
            _message = value;
            }
        }
protected void Page_Load(object sender, EventArgs e)
        {
        if (_Title != null)
            {
            lblModalTitle.Text = _Title;
            lblModalBody.Text = _message;
            ScriptManager.RegisterStartupScript(Page, Page.GetType(), "myModal", "$('#myModal').modal({backdrop: 'static',keyboard: false});", true);
            ScriptManager.RegisterStartupScript(Page, Page.GetType(), "myModal", "$('#myModal').on('shown.bs.modal', function () { $('#lblModalTitle').focus();})", true);
            upModal.Update();
            }
        }

Now I have aspx page. after the user clicks, server click event generates and after the operation ends I want to show popup with this user control.

what should I have to do that ? currently I implemented interface with method and overridden that method and accessed that in aspx page.