context.Response.Redirect(ConfigurationManager.AppSettings["URL"] + ext );

response.write("<script>");
response.write("window.open('page.html','_blank')");
response.write("</script>");

Response.Write("<script>window.open('http://www.somesite.com/','_blank');</script>");

<asp:Button runat="server" ID="cmd_Test" onclientclick="window.open('YourUrl')"  />

protected void Page_Load (object sender, EventArgs e)
{
    lnkViewPage.NavigateURL = sURL;
    lnkViewPage.Target = "_blank";
}

Response.Write("<script>window.open('page.html','_blank')</script>");

hyperlink1.Attributes.Add("onclick", "window.open(http://www.mylink.com?sessionvar1=" + someValue + "',null,'height=251px, width=600px,status=no, resizable=no, scrollbars=no, toolbar=no,location=no,menubar=no ');");

Response.Write("<script>")
Response.Write("window.open('NewPage.aspx','_blank','resizable=yes,scrollbars=yes,toolbar=yes,menubar=yes,location=no')")
Response.Write("</script>")