In this article I will explain with an example, how to call (execute) Server Side (Code Behind) method from jQuery UI Dialog Modal Popup in ASP.Net.
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Untitled Page</title>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
    <script src="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.9/jquery-ui.js" type="text/javascript"></script>
    <link href="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.9/themes/start/jquery-ui.css" rel="stylesheet" type="text/css" />
    <script type="text/javascript">
        $(function () {
            $("#dialog").dialog({
                buttons: {
                    Ok: function () {
                        $("[id*=Button1]").click();
                    },
                    Close: function () {
                        $(this).dialog('close');
                    }
                }
           });
        });
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div id="dialog" style="display:none">
    Click OK to do PostBack!
    </div>
    <asp:Button ID="Button1" runat="server" Text="Button" style = "display:none" OnClick = "Button1_Click" />
    </form>
</body>
</html>
 
Above I have a simple jQuery Dialog dialog which opens up as soon as the page is loaded. Just after the jQuery dialog I have placed a hidden ASP.Net Button Button1 which has a Click event handler assigned to it.
In the jQuery Dialog Initialization, I have specified two buttons
1. OK – Which when clicked makes the ASP.Net Button click and thus making a PostBack to the server which normally was not happening
2. Close – Which as the name suggests is a simple jQuery Dialog Button to close the Dialog.
 
Server side I have registered a script which will raise an alert when the Click event handler is executed.
protected void Button1_Click(object sender, EventArgs e)
{
    ClientScript.RegisterStartupScript(Page.GetType(), "key", "alert('Button Clicked')", true);
}
 
Demo
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