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File.WriteAllLines Method (String, IEnumerable<String>)

Creates a new file, writes a collection of strings to the file, and then closes the file.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

public static void WriteAllLines(
	string path,
	IEnumerable<string> contents


Type: System.String
The file to write to.
Type: System.Collections.Generic.IEnumerable<String>
The lines to write to the file.


path is a zero-length string, contains only white space, or contains one or more invalid characters defined by the GetInvalidPathChars method.


Either path or contents is null.


path is invalid (for example, it is on an unmapped drive).


The file specified by path was not found.


An I/O error occurred while opening the file.


path exceeds the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters and file names must be less than 260 characters.


path is in an invalid format.


The caller does not have the required permission.


path specifies a file that is read-only.


This operation is not supported on the current platform.


path is a directory.


The caller does not have the required permission.

If the target file already exists, it is overwritten.

You can use this method to create the contents for a collection class that takes an IEnumerable<T> in its constructor, such as a List<T>, HashSet<T>, or a SortedSet<T> class.

The following example writes selected lines from a sample data file to a file.

using System;
using System.IO;
using System.Linq;

class Program
	static string dataPath = @"c:\temp\timestamps.txt";

	static void Main(string[] args)

		var JulyWeekends = from line in File.ReadLines(dataPath)
						   where (line.StartsWith("Saturday") || 
						   line.StartsWith("Sunday")) & 
						   select line;

		File.WriteAllLines(@"C:\temp\selectedDays.txt", JulyWeekends);

		var MarchMondays = from line in File.ReadLines(dataPath)
						   where line.StartsWith("Monday") && 
						   select line;

		File.AppendAllLines(@"C:\temp\selectedDays.txt", MarchMondays);

	static void CreateSampleFile()
		DateTime TimeStamp = new DateTime(1700, 1, 1);

		using (StreamWriter sw = new StreamWriter(dataPath))
			for (int i = 0; i < 500; i++)
				DateTime TS1 = TimeStamp.AddYears(i);
				DateTime TS2 = TS1.AddMonths(i);
				DateTime TS3 = TS2.AddDays(i);

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.