How do I extract a chunk of text from a text file?

Question

I have a postscript file that has a starting indicator of where I want to begin copying data to a StringBuilder that reads:

$$StartCopy
$$ChunkID[1234]
$$Type[Foo]
\\bla bla for hundreds or thousands of lines
$$EndCopy  

$$StartCopy
$$ChunkID[4567]
$$Type[Bar]
\\bla bla for hundreds or thousands of lines
$$EndCopy 


$$StartCopy
$$ChunkID[4567]
$$Type[Foo]
\\bla bla for hundreds or thousands of lines
$$EndCopy

$$StartCopy
$$ChunkID[8901]
$$Type[Bar]
\\bla bla for hundreds or thousands of lines
$$EndCopy 

Note that there is no specific line that I can start at, nor is there any set number of lines between $$StartCopy and $$EndCopy. In this case, how do I grab the chunk of text $$Chunk[4567] where $$Type[Bar] from its start to end line?

To be clear, here is what the end result should be:

$$StartCopy
$$ChunkID[4567]
$$Type[Bar]
\\bla bla for hundreds or thousands of lines
$$EndCopy 

Answer 1

Since you are dealing with a large file and lots of results, it's probably better to use File.ReadLines which returns an IEnumerable<string> and an iterator method

/// <summary>
/// Will return the data from a file between the start and end parameters (inclusive)
/// </summary>
/// <param name="fileName">duh</param>
/// <param name="start">The start of the sequence</param>
/// <param name="end">The end of the sequence</param>
/// <returns>Stuff</returns>
public static IEnumerable<string> GetData(string fileName, string start, string end)
{
   var found = false;
   foreach (var line in File.ReadLines(fileName))
   {
      if (line == start) found = true;

      if (!found) continue;

      yield return line;

      if (line == end) break;
   }
}

Usage

var results = GetData(fileName, "$$StartCopy", "$$EndCopy");

_{Note : This code is completely untested and void of any warranty claims, take backs, or returns due to the people you may harm or otherwise maim with this code}

Great comment by Dai

The problem with NET's built-in ReadLine/ReadLineAsync/ReadLines methods is that they use the Environment.NewLine string and doesn't let you manually specify a line-terminator, making them useless for writing cross-platform code

Which is to say, this method really only deals with the following situations because of the inherent use of Environment.NewLine when determining what an actual line is.

A string containing "\r\n" for non-Unix platforms, or a string containing "\n" for Unix platforms.