You need a separate .cs file for each page. So you'll need to copy MiddlePage.cs to OtherPage.cs, AnotherPage.cs, YetAnotherPage.cs and then edit those separately.
Obviously, those are lousy names; you should name the pages based on what's on them. For example, you might have pages called UserDetailsPage.cs and DatabaseConnectionDetailsPage.cs, or whatever makes sense in your program.
You need to copy MiddlePage.cs
You need a separate .cs file for each page. So you'll need to copy MiddlePage.cs to OtherPage.cs, AnotherPage.cs, YetAnotherPage.cs and then edit those separately.
Obviously, those are lousy names; you should name the pages based on what's on them. For example, you might have pages called UserDetailsPage.cs and DatabaseConnectionDetailsPage.cs, or whatever makes sense in your program.