This was being called in Page_LoadComplete from autowire up,
protected void Page_LoadComplete(object sender, EventArgs e){
...
button.Click += new
EventHandler(button.OnClick);
...
}
once it is move into Page_Init method fires correctly
protected void Page_Init(object sender, EventArgs e){<br/>
...<br/>
button.Click += <span style="color:blue">new</span>
EventHandler(button.OnClick);<br/>
...<br/>
}