What's the fastest way to read a text file line-by-line?

Question

I want to read a text file line by line. I wanted to know if I\'m doing it as efficiently as possible within the .NET C# scope of things.

This is what I\'m trying so

Answer 1

While File.ReadAllLines() is one of the simplest ways to read a file, it is also one of the slowest.

If you're just wanting to read lines in a file without doing much, according to these benchmarks, the fastest way to read a file is the age old method of:

using (StreamReader sr = File.OpenText(fileName))
{
        string s = String.Empty;
        while ((s = sr.ReadLine()) != null)
        {
               //do minimal amount of work here
        }
}

However, if you have to do a lot with each line, then this article concludes that the best way is the following (and it's faster to pre-allocate a string[] if you know how many lines you're going to read) :

AllLines = new string[MAX]; //only allocate memory here

using (StreamReader sr = File.OpenText(fileName))
{
        int x = 0;
        while (!sr.EndOfStream)
        {
               AllLines[x] = sr.ReadLine();
               x += 1;
        }
} //Finished. Close the file

//Now parallel process each line in the file
Parallel.For(0, AllLines.Length, x =>
{
    DoYourStuff(AllLines[x]); //do your work here
});