File.WriteAllLines(String, IEnumerable<String>) Method in C# with Examples

File.WriteAllLines(String, IEnumerable<String>) is an inbuilt File class method that is used to create a new file, writes a collection of strings to the file, and then closes the file. Syntax:

public static void WriteAllLines (string path, System.Collections.Generic.IEnumerable<String>contents);

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

path: This is the specified file where collection of strings are going to be written.

contents: This is the specified lines to write to the file.

Exceptions:

ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters defined by the GetInvalidPathChars() method.
ArgumentNullException: Either path or contents are null.
DirectoryNotFoundException: The path is invalid.
IOException: An I/O error occurred while opening the file.
PathTooLongException: The path exceeds the system-defined maximum length.
NotSupportedException: The path is in an invalid format.
SecurityException: The caller does not have the required permission.
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 is a directory. OR the caller does not have the required permission.

Below are the programs to illustrate the File.WriteAllLines(String, IEnumerable) method. Program 1: Before running the below code, a file file.txt is created whose contents are going to be filtered that are shown below-

Below code, itself creates a new file gfg.txt which contains the filtered strings.

CSharp

// C# program to illustrate the usage
// of File.WriteAllLines(String, 
// IEnumerable<String>) method

// Using System, System.IO
// and System.Linq namespaces
using System;
using System.IO;
using System.Linq;

class GFG {
    // Specifying a file from where
    // some contents are going to be filtered
    static string Path = @"file.txt";

    static void Main(string[] args)
    {
        // Reading content of file.txt
        var da = from line in File.ReadLines(Path)

                 // Selecting lines started with "G"
                 where(line.StartsWith("G"))
                     select line;

        // Creating a new file gfg.txt with the
        // filtered contents
        File.WriteAllLines(@"gfg.txt", da);
        Console.WriteLine("Writing the filtered collection "+
                     "of strings to the file has been done.");
    }
}

Output:

Writing the filtered collection of strings to the file has been done.

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

Program 2: Before running the below code, two files file.txt and gfg.txt are created with some contents shown below-

Below code overwrites the file gfg.txt with the selected contents of the file file.txt.

CSharp

// C# program to illustrate the usage
// of File.WriteAllLines(String,
// IEnumerable<String>) method

// Using System, System.IO
// and System.Linq namespaces
using System;
using System.IO;
using System.Linq;

class GFG {
    // Specifying a file from where
    // some contents are going to be filtered
    static string Path = @"file.txt";

    static void Main(string[] args)
    {
        // Reading the contents of file.txt
        var da = from line in File.ReadLines(Path)

                 // Selecting lines started with "g"
                 where(line.StartsWith("g"))
                     select line;

        // Overwriting the file gfg.txt with the
        // selected string of the file file.txt
        File.WriteAllLines(@"gfg.txt", da);
        Console.WriteLine("Overwriting the selected collection"+
                      " of strings to the file has been done.");
    }
}

Output:

Overwriting the selected collection of strings to the file has been done.

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

File.WriteAllLines(String, IEnumerable<String>) Method in C# with Examples

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