On Button Click How Do I Call A Function And Redirect My Page To Different Site In Another Tab Of Browser

protected void ImageButton1_Click(object sender, EventArgs e)
        {
            string url = "Frm_report.aspx?ID=1&cat=test";
            string fullURL = "window.open('" + url + "', '_blank', 'height=500,width=800,status=yes,toolbar=no,menubar=no,location=no,scrollbars=yes,resizable=no,titlebar=no' );";
            Button1.Attributes.Add("OnClick", fullURL);
        }