How to read all lines from a file in C#
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The File class in the System.IO namespace provides the ReadAllLines() method, which is used to read all lines of a text file and return an array of strings containing all the lines of the file.
Syntax
public static string[] ReadAllLines (string filePath);
It takes the path of the file to read as an input and returns an array of strings.
The below scenarios are possible exceptions of this function:
- The input file path is null or empty, or has whitespace or invalid characters.
- The input file path or the file name is longer than the system-defined limit.
- The path is invalid or there is an IO error while opening or reading the file.
- The caller of the method does not have the right permission.
- The file is not found or represents a directory.
- The operation is not supported on the operating system.
Code example
In the following code example, a text file (test.txt) already exists in the current working directory. We will first check if this file exists, and then read all the lines of the file to a string array.
Finally, we will print this array of strings using the foreach loop.
The program will terminate after printing the output below:
first line of file
second line of file
third line of file
fourth line of file
fifth line of file
using System;using System.IO;class FileLineReader{public static void Main(){string filePath = @"test.txt";if(!File.Exists(filePath)){Console.WriteLine("File does not exist :{0} ", filePath);return;}string[] textFromFile = File.ReadAllLines(filePath);foreach (string line in textFromFile){Console.WriteLine(line);}}}
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Siddharth Singh