Rexexp. Big text with hierarchy

I have a text of law, with Chapters and Articles.

 Chapter 1. Something
 Article 1. trata-trata
 Article 2. trata-trata
 Article 3. trata-trata
 Chapter 2. Something
 Article 4. trata-trata
 Article 5. trata-trat开发者_运维百科a
 Article 6. trata-trata

I need regexp, to find Articles within Chapters, and know what articles belongs to what Chapter. (C# preferably)

Regex isn't best solution for your problem. You should to parse your text line by line and to store your Articles inside your Chapter structure.

string line = "";
StreamReader data = new StreamReader("your file.txt");
List<Chapter> chapters = new List<Chapter>();
while ((line = data.ReadLine()) != null)
{
    if (line.StartsWith("Chapter"))
    {
        chapters.Add(new Chapter(line));
    }
    else if (line.StartsWith("Article"))
    {
        chapters[chapters.Count - 1].Articles.Add(new Article(line));
    }
}