File.WriteAllLines Method (String, String[])

If the target file already exists, it is overwritten.

The default behavior of the WriteAllLines method is to write out data using UTF-8 encoding without a byte order mark (BOM). If it is necessary to include a UTF-8 identifier, such as a byte order mark, at the beginning of a file, use the WriteAllLines(String, String[], Encoding) method overload with UTF8 encoding.

Given a string array and a file path, this method opens the specified file, writes the string array to the file, and then closes the file.

The following code example demonstrates the use of the WriteAllLines method to write text to a file. In this example a file is created, if it doesn't already exist, and text is added to it.

using System;
using System.IO;
class Test
{
    public static void Main()
    {
        string path = @"c:\temp\MyTest.txt";

        // This text is added only once to the file.
        if (!File.Exists(path))
        {
            // Create a file to write to.
            string[] createText = { "Hello", "And", "Welcome" };
            File.WriteAllLines(path, createText);
        }

        // This text is always added, making the file longer over time
        // if it is not deleted.
        string appendText = "This is extra text" + Environment.NewLine;
        File.AppendAllText(path, appendText);

        // Open the file to read from.
        string[] readText = File.ReadAllLines(path);
        foreach (string s in readText)
        {
            Console.WriteLine(s);
        }
    }
}

.NET Framework

.NET Framework Client Profile

• FileIOPermission  

  for access to write to a file or directory. Associated enumeration: FileIOPermissionAccess.Write

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference