File.WriteAllLines(String, String[]) Method in C# with Examples

File.WriteAllLines(String, String[]) is an inbuilt File class method that is used to create a new file, writes the specified string array to the file, and then closes the file.

Syntax:

public static void WriteAllLines (string path, string[] contents);

Parameter: This function accepts two parameters which are illustrated below:

  • path: This is the specified file where specified string array are going to be written.
  • contents: This is the specified string array to write to the file.

Exceptions:

  • ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
  • ArgumentNullException: Either path or contents are 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 the path specified a file that is hidden. 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.
  • NotSupportedException: The path is in an invalid format.
  • SecurityException: The caller does not have the required permission.

Below are the programs to illustrate the File.WriteAllLines(String, String[]) method.



Program 1: Initially, no file was created. Below code itself create a file file.txt and write the specified string array into the file.

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// C# program to illustrate the usage
// of File.WriteAllLines(String,
// String[]) method
  
// Using System and System.IO,
// namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifing a file
        string path = @"file.txt";
  
        // Creating some string array to
        // write into the file
        string[] createText = { "GFG", "is a", "CS portal." };
  
        // Calling WriteAllLines() function to write
        // the specified string array into the file
        File.WriteAllLines(path, createText);
  
        // Reading the file contents
        string[] readText = File.ReadAllLines(path);
        foreach(string s in readText)
        {
            Console.WriteLine(s);
        }
    }
}

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Output:

GFG
is a
CS portal.

After running the above code, the above output is shown, and a new file file.txt is created shown below-

file.txt

Program 2: Initially, a file file.txt is created with some contents shown below-

file.txt

Below code overwrites the file contents with the specified string array.

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// C# program to illustrate the usage
// of File.WriteAllLines(String, 
// String[]) method
  
// Using System and System.IO,
// namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifing a file
        string path = @"file.txt";
  
        // Creating some string array to
        // write into the file
        string[] createText = { "GFG", "Geeks", "GeeksforGeeks" };
  
        // Calling WriteAllLines() function to overwrite
        // the specified string array into the file
        File.WriteAllLines(path, createText);
  
        // Reading the file contents
        string[] readText = File.ReadAllLines(path);
        foreach(string s in readText)
        {
            Console.WriteLine(s);
        }
    }
}

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Output:

GFG
Geeks
GeeksforGeeks

After running the above code, the above output is shown, and the file file.txt contents became like shown below:

file.txt




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