File.ReadAllLines(String) Method in C# with Examples

09 Mar, 2021
File.ReadAllLines(String) is an inbuilt File class method that is used to open a text file then reads all lines of the file into a string array and then closes the file.Syntax:  
public static string[] ReadAllLines (string path);
Parameter: This function accepts a parameter which is illustrated below:  
path: This is the specified file to open for reading.
Exceptions: 
ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
ArgumentNullException: The path is null.
PathTooLongException: The specified path, file name, or both exceed the system-defined maximum length.
DirectoryNotFoundException: The specified path is invalid.
IOException: An I/O error occurred while opening the file.
UnauthorizedAccessException: The path specified a file that is read-only. OR this operation is not supported on the current platform. OR the path specified a directory. OR the caller does not have the required permission.
FileNotFoundException: The file specified in the path was not found.
NotSupportedException: The path is in an invalid format.
SecurityException: The caller does not have the required permission.
Return Value: Returns a string array containing all lines of the file.Below are the programs to illustrate the File.ReadAllLines(String) method.Program 1: Initially, a file file.txt is created with some contents shown below- 
 
C#
// C# program to illustrate the usage// of File.ReadAllLines(String) method  // Using System, System.IO and// System.Text namespacesusing System;using System.IO;using System.Text;  class GFG {    public static void Main()    {        // Specifying a file        string path = @"file.txt";          // Calling the ReadAllLines() function        string[] readText = File.ReadAllLines(path);        foreach(string s in readText)        {            // Printing the string array containing            // all lines of the file.            Console.WriteLine(s);        }    }}
Output:  
GFG
Geeks
GeeksforGeeks
Program 2: Initially, no file was created. Below code itself create a file file.txt with some specified contents. 
C#
// C# program to illustrate the usage// of File.ReadAllLines(String) method  // Using System, System.IO and// System.Text namespacesusing System;using System.IO;using System.Text;  class GFG {    public static void Main()    {        // Specifying a file        string path = @"file.txt";          // Adding below contents to the file        string[] createText = { "GFG is a CS portal." };        File.WriteAllLines(path, createText);          // Calling the ReadAllLines() function        string[] readText = File.ReadAllLines(path);        foreach(string s in readText)        {            // Printing the string array containing            // all lines of the file.            Console.WriteLine(s);        }    }}
Output:  
GFG is a CS portal.
arorakashish0911
CSharp-File-Handling
C#
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