File.AppendAllLines(String, IEnumerable<String>, Encoding) Method in C# with Examples
Last Updated :
01 Jun, 2020
File.AppendAllLines(String, IEnumerable<String>, Encoding) is an inbuilt File class method which is used to append specified 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 new file, writes the specified lines to the file, and then closes the file.
Syntax:
public static void AppendAllLines (string path, System.Collections.Generic.IEnumerable<String> contents, System.Text.Encoding encoding);
Parameter: This function accepts two parameters which are illustrated below:
- path: This is the file where lines are going to be appended. The file is created if it doesn't already exist.
- contents: This is the specified contents which is to be appended to the file.
- encoding: This is the specified character encoding.
Exceptions:
- ArgumentException: The path is a zero-length string, contains only white space, or one more invalid characters defined by the GetInvalidPathChars() method.
- ArgumentNullException: Either path, contents, or encoding is null.
- DirectoryNotFoundException: The path is invalid i.e, the directory doesn't exist or it is on an unmapped drive.
- FileNotFoundException: The file given by the path was not found.
- IOException: An I/O error occurred while opening the file.
- PathTooLongException: The path exceeds the system-defined maximum length.
- NotSupportedException: The path is in an invalid format.
- SecurityException: The caller does not have the required permission.
- UnauthorizedAccessException: The path specifies a file that is read-only. OR This operation is not supported on the current platform. OR the path is a directory. OR the caller does not have the required permission.
Below are the programs to illustrate the File.AppendAllLines(String, IEnumerable, Encoding) method.
Program 1: There is two files used one is
file.txt and another one is
gfg.txt whose contents are shown below before running the program.
CSharp
// C# program to illustrate the usage
// of File.AppendAllLines() method
// Using System, System.IO,
// System.Linq and System.Text namespaces
using System;
using System.IO;
using System.Linq;
using System.Text;
// Creating class
class GfG {
// Creating a file
static string myfile = @"file.txt";
// Main method
static void Main(string[] args)
{
// Reading lines of the file created above
var appendTofile = from line in File.ReadLines(myfile)
// Using select statement
select line;
// Calling AppendAllLines() method with its
// parameters
File.AppendAllLines(@"gfg.txt", appendTofile, Encoding.UTF8);
// Printed when the stated file is appended
Console.WriteLine("All lines are appended");
}
}
mcs -out:main.exe main.cs
mono main.exe
All lines are appended
After running the above code, above output will be shown and content of the file
gfg.txt will be like shown below, that means contents of
file.txt have been appended to the file
gfg.txt
Program 2: There is only one file
file.txt has been created whose contents are shown below:
CSharp
// C# program to illustrate the usage
// of File.AppendAllLines() method
// Using System, System.IO,
// System.Linq and System.Text namespaces
using System;
using System.IO;
using System.Linq;
using System.Text;
// Creating class
class GfG {
// Creating a file
static string myfile = @"file.txt";
// Main method
static void Main(string[] args)
{
// Reading lines of the file created above
var appendTofile = from line in File.ReadLines(myfile)
// It only appends the line that starts with g
where(line.StartsWith("g"))
// Using select statement
select line;
// Calling AppendAllLines() method with its
// parameters
File.AppendAllLines(@"gfg.txt", appendTofile, Encoding.UTF8);
// Printed when the stated file is appended
Console.WriteLine("All lines are appended");
}
}
mcs -out:main.exe main.cs
mono main.exe
All lines are appended
After running the above code, above output will be shown and it will create a new file called
gfg.txt having contents same as file
file.txt:
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