Where to store URL name and path

I am creating a web application.
I am using Response.Redirect("~/mypage1.aspx")
I want to change it to  Response.Redirect(mypage1url); 
But where to define all the ULRs so that I can manage  like URL
  name=mypage1url path="~/mypage1.aspx" .
If I am using xml file what is the suggested format.
Or should I have just a file with all ULRS vairables like String mypage1URL ="~/mypage1.aspx";
string myPage1Url = "/mypage1.aspx?MyCell=" + strCell;
string mypage2URL = "mypage2.aspx";
 
 
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