File.AppendAllLines
Method
Definition
Overloads
| AppendAllLines(String, IEnumerable<String>) |
Appends lines to a file, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file. |
| AppendAllLines(String, IEnumerable<String>, Encoding) |
Appends lines to a file by using a specified encoding, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file. |
AppendAllLines(String, IEnumerable<String>)
Appends lines to a file, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file.
public static void AppendAllLines (string path, System.Collections.Generic.IEnumerable<string> contents);
- path
- String
The file to append the lines to. The file is created if it doesn't already exist.
- contents
- IEnumerable<String>
The lines to append to the file.
path is a zero-length string, contains only white space, or contains one more invalid characters defined by the GetInvalidPathChars() method.
Either path or contents is null.
path is invalid (for example, the directory doesn’t exist or 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 permission to write to the file.
path specifies a file that is read-only.
-or-
This operation is not supported on the current platform.
-or-
path is a directory.
Examples
The following example writes selected lines from a sample data file to a file, and then appends more lines. The directory named temp on drive C must exist for the example to complete successfully.
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 method creates the file if it doesn’t exist, but it doesn't create new directories. Therefore, the value of the path parameter must contain existing directories.
AppendAllLines(String, IEnumerable<String>, Encoding)
Appends lines to a file by using a specified encoding, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file.
public static void AppendAllLines (string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding);
- path
- String
The file to append the lines to. The file is created if it doesn't already exist.
- contents
- IEnumerable<String>
The lines to append to the file.
- encoding
- Encoding
The character encoding to use.
path is a zero-length string, contains only white space, or contains one more invalid characters defined by the GetInvalidPathChars() method.
Either path, contents, or encoding is null.
path is invalid (for example, the directory doesn’t exist or 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.
-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
The method creates the file if it doesn’t exist, but it doesn't create new directories. Therefore, the value of the path parameter must contain existing directories.
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.