Last few months, I got a problem to place a button to generate a CSV file in the update panel. I was having a problem related with response error. So what i did was to place the button outside the Update Panel. Today, I found a simple solution to place this button inside the AJAX Update panel

1. You need to set the page mode on the page load event

protected void Page_Load(object sender, EventArgs e)
{
    this.Page.Form.Enctype = "multipart/form-data";
}

2. set the update Panel Children as trigger to true

3. set the trigger to your button