open popup window in button click event without using jquery

public partial class specialitymaster : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void btnOpenPopupWindow_Click(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

}

}

 

i just tried simply. i designed one button and one popup window.if i click open popup window in button click event i need to open popup window. i donno it is possible or not.i created button click event in CS page but i donno how to call that popup window name in button click event .