MultiLine Textbox Question

I have a MultiLine Textbox where the user would put in a string of
Unique IDs, where each Unique ID is in a separate row or line.

I want to take each row and add each value into an array.

How do I read each row in a MultiLine TextBox?

Do I go character by character? If so, what character should I be
testing for when I get to the end of a line?

Thanks in advance!
JJ