How to Read a text file line by line in C#

• File.ReadLines(): Reads small chunks of the file into memory (buffering) and gives you one line at a time.
• File.ReadAllLines(): Reads the entire file into a string array (one string per line).

Using File.ReadLines() to read a file line by line

This method reads the file incrementally, one line at a time, which makes it memory-efficient.

using System.IO;

foreach (var line in File.ReadLines(@"C:\temp\fruits.txt"))
{
    Console.WriteLine(line);
}

Output:

apple
banana
cherry

Using File.ReadAllLines() to read the entire file into an array

In this case, the entire content of the file is loaded into an array, where each line is an element.

using System.IO;

string[] lines = File.ReadAllLines(@"C:\temp\fruits.txt");

foreach (var line in lines)
{
    Console.WriteLine(line);
}

Output:

apple
banana
cherry

Skip the first line using File.ReadLines()

To skip the first line while reading the file, use the LINQ method Skip(1).

using System.IO;
using System.Linq;

foreach (var line in File.ReadLines(@"C:\temp\fruits.txt").Skip(1))
{
    Console.WriteLine(line);
}

Output:

banana
cherry

Read just the first line using File.ReadLines()

If you only want the first line of the file, use Take(1) from LINQ.

using System.IO;
using System.Linq;

foreach (var line in File.ReadLines(@"C:\temp\fruits.txt").Take(1))
{
    Console.WriteLine(line);
}

Output:

apple

Read a file line by line asynchronously with File.ReadLinesAsync()

For asynchronous reading, you can use File.ReadLinesAsync(). This was introduced in .NET 7 and returns an IAsyncEnumerable.

using System.IO;

await foreach (var line in File.ReadLinesAsync(@"C:\temp\fruits.txt"))
{
    Console.WriteLine(line);
}

apple
banana
cherry

These methods provide various ways to read files efficiently, depending on your needs.