StreamReader and seeking

Question

can you use streamreader to read a normal textfile and then in the middle of reading close the streamreader after saving the current position and then open streamreader agai

Answer 1

FileStream.Position (or equivalently, StreamReader.BaseStream.Position) will usually be ahead -- possibly way ahead -- of the TextReader position because of the underlying buffering taking place.

If you can determine how newlines are handled in your text files, you can add up the number of bytes read based on line lengths and end-of-line characters.

File.WriteAllText("test.txt", "1234" + System.Environment.NewLine + "56789");

long position = -1;
long bytesRead = 0;
int newLineBytes = System.Environment.NewLine.Length;

using (var sr = new StreamReader("test.txt"))
{
    string line = sr.ReadLine();
    bytesRead += line.Length + newLineBytes;

    Console.WriteLine(line);

    position = bytesRead;
}

Console.WriteLine("Wait");

using (var sr = new StreamReader("test.txt"))
{
    sr.BaseStream.Seek(position, SeekOrigin.Begin);
    Console.WriteLine(sr.ReadToEnd());
}

For more complex text file encodings you might need to get fancier than this, but it worked for me.