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.

C#

// 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()
    {
        // Specifying 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);
        }
    }
}

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-

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

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

C#

// 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()
    {
        // Specifying 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);
        }
    }
}

Output:

GFG
Geeks
GeeksforGeeks

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