File.WriteAllLines Method (String, IEnumerable(Of String))


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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 Shared Sub WriteAllLines (
	path As String,
	contents As IEnumerable(Of String)


Type: System.String

The file to write to.

Type: System.Collections.Generic.IEnumerable(Of String)

The lines to write to the file.

Exception Condition

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).


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.

The default behavior of the WriteAllLines(String, IEnumerable(Of String)) method is to write out data by 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, IEnumerable(Of String), Encoding) method overload with UTF8 encoding.

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(Of T) in its constructor, such as a List(Of T), HashSet(Of T), or a SortedSet(Of T) class.

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

Imports System
Imports System.IO
Imports System.Linq

Class Program
    Shared dataPath As String = "c:\temp\timestamps.txt"

    Public Shared Sub Main(ByVal args As String())

        Dim JulyWeekends = From line In File.ReadLines(dataPath) _
            Where (line.StartsWith("Saturday") OrElse _
            line.StartsWith("Sunday")) And line.Contains("July") _
            Select line

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

        Dim MarchMondays = From line In File.ReadLines(dataPath) _
            Where line.StartsWith("Monday") AndAlso line.Contains("March") _
            Select line

        File.AppendAllLines("C:\temp\selectedDays.txt", MarchMondays)
    End Sub

    Private Shared Sub CreateSampleFile()
        Dim TimeStamp As New DateTime(1700, 1, 1)

        Using sw As New StreamWriter(dataPath)
            For i As Integer = 0 To 499
                Dim TS1 As DateTime = TimeStamp.AddYears(i)
                Dim TS2 As DateTime = TS1.AddMonths(i)
                Dim TS3 As DateTime = TS2.AddDays(i)

        End Using
    End Sub
End Class

Universal Windows Platform
Available since 10
.NET Framework
Available since 4.0
Available since 4.0
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