C# :: Button Taking To Another Page

I decided to code my own GUI menu. getting to another page from a button click. I have added the event handler I think (click="Button_click") then in the event handler I have added this:

private void Button_Click(object sender, System.EventArgs e);
}
Response.Redirect("Login.xaml");
}

After researching it says either to use
Response.Redirect("Login.xaml");
OR
Server.Transfer("Login.xaml");
Neither of these work, underlining "Response" and "Server" as an error saying "A namespace cannot directly contain members such as fields or methods."

NOTE: MY MAIN GUI PAGE IS CALLED "mainpage.xaml" THE CODE ABOVE IS STORED IN THE "mainpage.xaml.cs" THIS MIGHT BE RIGHT OR WRONG BUT I'M NOT SURE SO I AM LEAVING SOME EXTRA INFO!