C# Program to Count the Number of Lines in a File

Firstly, create a file using StreamWriter class and add content to it −

using (StreamWriter sw = new StreamWriter("hello.txt")) {
   sw.WriteLine("This is demo line 1");
   sw.WriteLine("This is demo line 2");
   sw.WriteLine("This is demo line 3");
}

Now use the ReadAllLines() method to read all the lines. With that, the Length property is to be used to get the count of lines −

int count = File.ReadAllLines("hello.txt").Length;

Here is the complete code −

Example

 Live Demo

using System;
using System.Collections.Generic;
using System.IO;
public class Program {
   public static void Main() {
      using (StreamWriter sw = new StreamWriter("hello.txt")) {
         sw.WriteLine("This is demo line 1");
         sw.WriteLine("This is demo line 2");
         sw.WriteLine("This is demo line 3");
      }
      int count = File.ReadAllLines("hello.txt").Length;
      Console.WriteLine("Number of lines: "+count);
   }
}

Output

Number of lines: 3