It's not entirely clear if you're specifically looking for ...
1) a generic line of text that has had a newline inserted in the middle, or
2) if you're actually referring to something like multiple C# statements that used to be defined on one line now being split into separate lines.
To just detect if a line of text was split, you should be able to look at the line of text before the edit and compare it to the same line after the edit. A text snapshot (ITextSnapshot) is captured for every version of document, so you should be able to use the snapshot before the edit to get the line content prior to the edit.
To detect a C# statement split would be more complex. You'd still use a text snapshot to get the line that was edited (like in the prior paragraph), but you'd then have to query the old abstract syntax tree (AST) to find statements on that line and compare it to statements on the new AST after the edit.
Please note that in your original post about "I don't care if this scenario occors" it appears the before and after text are the same ("int a = 2;" in both examples), so not sure what you are trying to illustrate there.
The following help topic goes into more depth on working with snapshots if needed: