vb Code:
  1. Private Sub RichTextBox1_EnterKeyPressed(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles RichTextBox1.KeyDown
  2.         Dim numlinecount As Integer
  3.         If e.KeyData = Keys.Enter Then
  4.             numlinecount = (RichTextBox2.GetLineFromCharIndex(RichTextBox2.Text.Length)) + 1
  5.             RichTextBox2.AppendText(CStr(numlinecount) & vbLf)
  6.         End If
  7.     End Sub

Option strict is almost always on for me, because I like to know how the conversions are with my application to reduce any conversion conflictions as well.

Here's my current code so far where rtb1 is the main editor, and rtb2 is the line display on the left side like in notepad++. So far my code allows for a number to be added on a new line in the line display when the enter key is pressed, however I want to know how I can get rid of those numbers whenever a backspace or deleted selection of text or the delete key erases a {vbLf} entry in rtb1 so that I can remove the integers on the left side accordingly to keep up with an accurate line count display. Also adding the number of "lines" (as integers/numbers) to that left hand display depending on how many {vbLf} entries there are in a pasted clipboard.

Then that should cover everything about the line display, except for loading a document and automatically displaying the number of lines in the text. I believe i'd have to count the number of occurences of {vbLf} upon opening a document, but I haven't tried yet, so i'm not sure how slow or fast that would render opening a document.