c# how do I count lines in a textfile

Question

any problems with doing this?

int  i = new StreamReader(\"file.txt\").ReadToEnd().Split(new char[] {\'\\n\'}).Length

Answer 1

The method you posted isn't particularly good. Lets break this apart:

// new StreamReader("file.txt").ReadToEnd().Split(new char[] {'\n'}).Length
//     becomes this:
var file = new StreamReader("file.txt").ReadToEnd(); // big string
var lines = file.Split(new char[] {'\n'});           // big array
var count = lines.Count;

You're actually holding this file in memory twice: once to read all the lines, once to split it into an array. The garbage collector hates that.

If you like one liners, you can write System.IO.File.ReadAllLines(filePath).Length, but that still retrieves the entire file in an array. There's no point doing that if you aren't going to hold onto the array.

A faster solution would be:

int TotalLines(string filePath)
{
    using (StreamReader r = new StreamReader(filePath))
    {
        int i = 0;
        while (r.ReadLine() != null) { i++; }
        return i;
    }
}

The code above holds (at most) one line of text in memory at any given time. Its going to be efficient as long as the lines are relatively short.