vb.net regex parse paragraph from report - regex

Question

I have a report I am given in plain text that a coworker typically has to manually edit out various headers. I know the top line and bottom line of the header - they do not differ throughout the document, but the various lines of text between does.
Formatting looks like this:
BEGIN REPORT FOR CLIENT XXYYZZ
RANDOM BODY TEXT
RANDOM BODY TEXT
RANDOM BODY TEXT
RANDOM BODY TEXT
RANDOM BODY TEXT
FINAL REPORT
I am attempting to use regular expressions to highlight this text within a rich text box. If I use the below code I can highlight every occurrence of the top line without issue:
Dim mystring As String = "(BEGIN)(.+?)(XXYYZZ)"
Dim regHeader As New Regex(mystring)
Dim regMatch As Match = regHeader.Match(rtbMain.Text)
While regMatch.Success
rtbMain.Select(regMatch.Index, regMatch.Length)
rtbMain.SelectionColor = Color.Blue
regMatch = regMatch.NextMatch()
End While
However, once I attempt to change the code to find the entire paragraph it no longer will highlight anything. Below is what I was expecting it to be but it does not seam to like it for whatever reason and will not highlight anything:
Dim mystring As String = "(BEGIN REPORT FOR CLIENT XXYYZZ)(.+?)(FINAL REPORT)"
Dim regHeader As New Regex(mystring)
Dim regMatch As Match = regHeader.Match(rtbMain.Text)
While regMatch.Success
rtbMain.Select(regMatch.Index, regMatch.Length)
rtbMain.SelectionColor = Color.Blue
regMatch = regMatch.NextMatch()
End While
Any help would be greatly appreciated.

Answer 1

What you need is singleline mode, in order to let . match even newlines.
Try this:
Dim mystring As String = "(BEGIN REPORT FOR CLIENT XXYYZZ)(.+?)(FINAL REPORT)"
Dim regHeader As New Regex(mystring, RegexOptions.Singleline)
Dim regMatch As Match = regHeader.Match(rtbMain.Text)
While regMatch.Success
rtbMain.Select(regMatch.Index, regMatch.Length)
rtbMain.SelectionColor = Color.Blue
regMatch = regMatch.NextMatch()
End While
Notice RegexOptions.Singleline.