CODEWITHSUNDEEP
c#regex
zooid
zooid

Reputation: 101

How to implement multi line comment block

I've been investigating ways to implement a code highlighting text editor and came across this example: https://archive.codeplex.com/?p=syntaxhighlightbox

However I cannot figure out how to implement multi-line block of comments or strings:

They use this to comment complete lines:

//
                // LINES RULES
                //
                foreach (HighlightLineRule rule in lineRules) {
                    Regex lineRgx = new Regex(Regex.Escape(rule.LineStart) + ".*");
                    foreach (Match m in lineRgx.Matches(text.Text)) {
                        text.SetForegroundBrush(rule.Options.Foreground, m.Index, m.Length);
                        text.SetFontWeight(rule.Options.FontWeight, m.Index, m.Length);
                        text.SetFontStyle(rule.Options.FontStyle, m.Index, m.Length);
                    }
                }

I tried changing it to:

Regex lineRgx = new Regex(Regex.Escape(rule.LineStart) + ".*" + Regex.Escape(rule.LineStart));

And although it works using the comment sign on both ends, it doesn't work for multi-line block

Could anyone suggest a solution or point me out for a beginner explanation of this regex as my knowledge of C# is limited and I didn't know about regex before seeing this project.

Upvotes: 0

Views: 143

Answers (1)

Ryszard Czech
Ryszard Czech

Reputation: 18611

".*" is a) greedy, b) stumbles on line endings.

Use

Regex lineRgx = new Regex(Regex.Escape(rule.LineStart) + "(?s).*?(?-s)" + Regex.Escape(rule.LineStart));

No need adding extra options.

EXPLANATION

----------------------------------------------------------------------------------------------
(?s)                           enable . to match line ending characters
----------------------------------------------------------------------------------------------
.*?                             any character (0 or more times
                               (matching the least amount possible))
----------------------------------------------------------------------------------------------
(?-s)                           disable . to match line ending characters

Upvotes: 2

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