Hi.

My simple requirement: Reading a huge (> a million) line test file (For this example assume it's a CSV of some sorts) and keeping a reference to the beginning of that line for faster lookup in the future (read a line, starting at X).

I tried the naive and easy way first, using a StreamWriter and accessing the underlying BaseStream.Position. Unfortunately that doesn't work as I intended:

Given a file containing the following

Foo
Bar
Baz
Bla
Fasel

and this very simple code

using (var sr = new StreamReader(@"C:\Temp\LineTest.txt")) {
  string line;
  long pos = sr.BaseStream.Position;
  while ((line = sr.ReadLine()) != null) {
    Console.Write("{0:d3} ", pos);
    Console.WriteLine(line);
    pos = sr.BaseStream.Position;
  }
}

the output is:

000 Foo
025 Bar
025 Baz
025 Bla
025 Fasel

I can imagine that the stream is trying to be helpful/efficient and probably reads in (big) chunks whenever new data is necessary. For me this is bad..

The question, finally: Any way to get the (byte, char) offset while reading a file line by line without using a basic Stream and messing with \r \n \r\n and string encoding etc. manually? Not a big deal, really, I just don't like to build things that might exist already..