How to create Reponse.Redirect open with new window...c# .net

I am working on a C# .net application in which I need to open a new browser and direct users to it in the event they click on a button or image.

i want to keep the main page and opens a new window browser once the user click the button.
here's my code.
aspx page.
<asp:Button ID="previewbtn" runat="server" Text="PREVIEW " OnClick="previewbtn_Click" />
code behind:
Response.Redirect("newpage.aspx?bg=" + Session["user"].ToString() + "&dc=" + Session["dcode"].ToString());
...