File.WriteAllLines
Method
Definition
Overloads
| WriteAllLines(String, String[], Encoding) |
Creates a new file, writes the specified string array to the file by using the specified encoding, and then closes the file. |
| WriteAllLines(String, IEnumerable<String>, Encoding) |
Creates a new file by using the specified encoding, writes a collection of strings to the file, and then closes the file. |
| WriteAllLines(String, String[]) |
Creates a new file, write the specified string array to the file, and then closes the file. |
| WriteAllLines(String, IEnumerable<String>) |
Creates a new file, writes a collection of strings to the file, and then closes the file. |
WriteAllLines(String, String[], Encoding)
Creates a new file, writes the specified string array to the file by using the specified encoding, and then closes the file.
public static void WriteAllLines (string path, string[] contents, System.Text.Encoding encoding);
- path
- String
The file to write to.
- contents
- String[]
The string array to write to the file.
- encoding
- Encoding
An Encoding object that represents the character encoding applied to the string array.
path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.
Either path or contents is null.
The specified path, file name, or both exceed 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.
The specified path is invalid (for example, it is on an unmapped drive).
An I/O error occurred while opening the file.
path specified a file that is read-only.
-or-
This operation is not supported on the current platform.
-or-
path specified a directory.
-or-
The caller does not have the required permission.
path is in an invalid format.
The caller does not have the required permission.
Examples
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;
using System.Text;
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, Encoding.UTF8);
}
// 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, Encoding.UTF8);
// Open the file to read from.
string[] readText = File.ReadAllLines(path, Encoding.UTF8);
foreach (string s in readText)
{
Console.WriteLine(s);
}
}
}
Imports System
Imports System.IO
Imports System.Text
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
Dim sw As StreamWriter
' This text is added only once to the file.
If File.Exists(path) = False Then
' Create a file to write to.
Dim createText() As String = {"Hello", "And", "Welcome"}
File.WriteAllLines(path, createText, Encoding.UTF8)
End If
' This text is always added, making the file longer over time
' if it is not deleted.
Dim appendText As String = "This is extra text" + Environment.NewLine
File.AppendAllText(path, appendText, Encoding.UTF8)
' Open the file to read from.
Dim readText() As String = File.ReadAllLines(path, Encoding.UTF8)
Dim s As String
For Each s In readText
Console.WriteLine(s)
Next
End Sub
End Class
Remarks
If the target file already exists, it is overwritten.
Given a string array and a file path, this method opens the specified file, writes the string array to the file using the specified encoding, and then closes the file.
WriteAllLines(String, IEnumerable<String>, Encoding)
Creates a new file by using the specified encoding, writes a collection of strings to the file, and then closes the file.
public static void WriteAllLines (string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding);
- path
- String
The file to write to.
- contents
- IEnumerable<String>
The lines to write to the file.
- encoding
- Encoding
The character encoding to use.
path is a zero-length string, contains only white space, or contains one or more invalid characters defined by the GetInvalidPathChars() method.
Either path, contents, or encoding 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.
-or-
This operation is not supported on the current platform.
-or-
path is a directory.
-or-
The caller does not have the required permission.
Remarks
If the target file already exists, it is overwritten.
You can use this method to create a file that contains the following:
The results of a LINQ to Objects query on the lines of a file, as obtained by using the ReadLines method.
The contents of a collection that implements an IEnumerable<T> of strings.
WriteAllLines(String, String[])
Creates a new file, write the specified string array to the file, and then closes the file.
public static void WriteAllLines (string path, string[] contents);
- path
- String
The file to write to.
- contents
- String[]
The string array to write to the file.
path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.
Either path or contents is null.
The specified path, file name, or both exceed 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.
The specified path is invalid (for example, it is on an unmapped drive).
An I/O error occurred while opening the file.
path specified a file that is read-only.
-or-
This operation is not supported on the current platform.
-or-
path specified a directory.
-or-
The caller does not have the required permission.
path is in an invalid format.
The caller does not have the required permission.
Examples
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);
}
}
}
Imports System
Imports System.IO
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
Dim sw As StreamWriter
' This text is added only once to the file.
If File.Exists(path) = False Then
' Create a file to write to.
Dim createText() As String = {"Hello", "And", "Welcome"}
File.WriteAllLines(path, createText)
End If
' This text is always added, making the file longer over time
' if it is not deleted.
Dim appendText As String = "This is extra text" + Environment.NewLine
File.AppendAllText(path, appendText)
' Open the file to read from.
Dim readText() As String = File.ReadAllLines(path)
Dim s As String
For Each s In readText
Console.WriteLine(s)
Next
End Sub
End Class
Remarks
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.
WriteAllLines(String, IEnumerable<String>)
Creates a new file, writes a collection of strings to the file, and then closes the file.
public static void WriteAllLines (string path, System.Collections.Generic.IEnumerable<string> contents);
- path
- String
The file to write to.
- contents
- 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).
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.
-or-
This operation is not supported on the current platform.
-or-
path is a directory.
-or-
The caller does not have the required permission.
Examples
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)
{
CreateSampleFile();
var JulyWeekends = from line in File.ReadLines(dataPath)
where (line.StartsWith("Saturday") ||
line.StartsWith("Sunday")) &
line.Contains("July")
select line;
File.WriteAllLines(@"C:\temp\selectedDays.txt", JulyWeekends);
var MarchMondays = from line in File.ReadLines(dataPath)
where line.StartsWith("Monday") &&
line.Contains("March")
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);
sw.WriteLine(TS3.ToLongDateString());
}
}
}
}
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())
CreateSampleFile()
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)
sw.WriteLine(TS3.ToLongDateString())
Next
End Using
End Sub
End Class
Remarks
The default behavior of the WriteAllLines(String, IEnumerable<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<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<T> in its constructor, such as a List<T>, HashSet<T>, or a SortedSet<T> class.