Button Click automatically not triggering - asp.net

Question

I have a button,Linkbutton and an ModalPopup.
If I click button1 I need to click 2nd button automatically and Launch ModalPopup.But it's not triggering at all.
Can anyone say me where am I going wrong?
This is my ModalPopup:
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="LinkButton1"
PopupControlID="Panel1" BackgroundCssClass="modalBackground" DropShadow="False"
CancelControlID="CancelButton" />
<asp:Panel ID="Panel1" runat="server" CssClass="modalPopup" Style="display: none;
width: 300px;">
<asp:HyperLink ID="DownloadLink" runat="server" ForeColor="#0066FF">Download</asp:HyperLink>
<asp:Button ID="CancelButton" CssClass="btn-blue" runat="server" Text="Cancel" />
<asp:Button ID="button1" runat="server" Text="Select Image" Style="position: absolute;
left: 400px; top: 500px; z-index: 99;"/>
<asp:LinkButton ID="LinkButton1" OnClick="LinkButton1_Click" runat="server" Visible="true"
Style="position: absolute; left: 620px; top: 500px; z-index: 99;">Close</asp:LinkButton>
</asp:Panel>
<br />
</ContentTemplate>
</asp:UpdatePanel>
This is my code-behind:
1st Button:
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
Linkbutton1_Click(Nothing,Nothing)
End Sub
2nd Button:
Protected Sub Linkbutton1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles
Linkbutton1.Click
ModalPopupExtender1.Show
End Sub

Answer 1

Unless there's something I'm missing, the approach you're using seems unnecessarily complicated. Just create a method that opens the dialog, and you can call it anywhere...
protected void LinkButton1_Click(object sender, EventArgs e)
{
//perform whatever logic you need
//open the dialog
ShowDialog();
}
protected void Button1_Click(object sender, EventArgs e)
{
//perform whatever logic you need
//open the dialog
ShowDialog();
}
private void ShowDialog()
{
ModalPopupExtender1.Show();
}

Answer 2

Give this a try. For code within the first button click.
Linkbutton1_Click(sender, New System.EventArgs())