JavaScriptConfirm.aspx.cs

public partial class JavaScriptConfirm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // wire the client side onclick to TestButton4
        this.TestButton4.Attributes.Add("onclick", "return AreYouSure();");

        if(Page.IsPostBack)
        {
            Response.Write
            (
                String.Format("Page_Load, IsPostBack: {0}<hr>", DateTime.Now.ToLongTimeString())
            );
        }
    }

    // the server side 'event' kicked off when asp:button is clicked
    protected void InvokeServerSideMethod(object sender, EventArgs e)
    {
        Response.Write
        (
            String.Format("InvokeServerSideMethod, E: {0}<hr>", DateTime.Now.ToLongTimeString())
        );
    }
}