File Class

Namespace: System.IO

Provides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of Stream objects.

Methods

AppendAllLines (string path, IEnumerable<string> contents)

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 contents to the file, and then closes the file.
AppendAllText (string path, string contents)

Appends specified data to the end of the specified file. If the file does not exist, this method creates it.
AppendText (string path)

Opens a file or creates a new file to write UTF-8 encoded text to.
Copy (string sourceFileName, string destinationFileName)

Copies an existing file to a new location.
Create (string path)

Creates or overwrites a file in the specified path.
Delete (string path)

Deletes the specified file.
Exists (string path)

Determines whether the specified file exists.
ReadAllBytes (string path)

Opens a binary file, reads the contents of the file into a byte array, and then closes the file.
ReadAllLines (string path)

Opens a text file, reads all lines of the file, and then closes the file.
ReadAllText (string path)

Opens a text file, reads all lines of the file, and then closes the file.
WriteAllBytes (string path, byte[] bytes)

Creates a new file, writes the specified byte array to the file, and then closes the file. If the target file already exists, it is overwritten.
WriteAllLines (string path, IEnumerable<string> contents)

Creates a new file, writes a collection of strings to the file, and then closes the file.
WriteAllText (string path, string contents)

Creates a new file, writes the specified string to the file, and then closes the file. If the target file already exists, it is overwritten.

AppendAllLines

AppendAllLines (string path, IEnumerable<string> contents)

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 contents to the file, and then closes the file.

Parameters

path: The file to append to.
contents: The lines to append to the file.

using System;
using System.IO;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\MyFile.txt";
        var lines = new List<string>() { "This is the first line.", "This is the second line." };

        // Append the lines to the file.
        File.AppendAllLines(path, lines);

        // Append more lines.
        var moreLines = new List<string>() { "This is a third line.", "And a fourth." };
        File.AppendAllLines(path, moreLines);

        Console.WriteLine($"Lines appended to {path}");
    }
}

AppendAllText

AppendAllText (string path, string contents)

Appends specified data to the end of the specified file. If the file does not exist, this method creates it.

Parameters

path: The file to append to.
contents: The string to append to the file.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\MyFile.txt";
        string textToAppend = "\nThis text will be appended.";

        // Append the text to the file.
        File.AppendAllText(path, textToAppend);

        Console.WriteLine($"Text appended to {path}");
    }
}

AppendText

AppendText (string path)

Opens a file or creates a new file to write UTF-8 encoded text to.

Parameters

path: The path of the file to append to.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\MyFile.txt";

        // Open the file for appending text.
        using (StreamWriter sw = File.AppendText(path))
        {
            sw.WriteLine("Appending this line.");
            sw.WriteLine("And another one.");
        }

        Console.WriteLine($"Text appended to {path} using StreamWriter.");
    }
}

Copy

Copy (string sourceFileName, string destinationFileName)

Copies an existing file to a new location.

Parameters

sourceFileName: The path of the file to copy.
destinationFileName: The destination path to copy the file to.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string sourcePath = @"C:\temp\Original.txt";
        string destinationPath = @"C:\temp\Copied.txt";

        // Create a dummy source file if it doesn't exist
        if (!File.Exists(sourcePath))
        {
            File.WriteAllText(sourcePath, "This is the content of the original file.");
        }

        // Copy the file.
        File.Copy(sourcePath, destinationPath);

        Console.WriteLine($"File copied from {sourcePath} to {destinationPath}");
    }
}

Create

Create (string path)

Creates or overwrites a file in the specified path. The current file is overwritten if the file exists, and a new file is created if the file does not exist.

Parameters

path: The name of the file to create.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\NewFile.txt";

        // Create a new file. If it exists, it will be overwritten.
        using (FileStream fs = File.Create(path))
        {
            // You can write to the file stream here if needed
            byte[] content = new byte[] { 0x48, 0x65, 0x6c, 0x6c, 0x6f }; // "Hello"
            fs.Write(content, 0, content.Length);
        }

        Console.WriteLine($"File created or overwritten at {path}");
    }
}

Delete

Delete (string path)

Deletes the specified file.

Parameters

path: The name of the file to be deleted.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\FileToDelete.txt";

        // Create a dummy file to delete
        File.WriteAllText(path, "This file will be deleted.");

        if (File.Exists(path))
        {
            // Delete the file.
            File.Delete(path);
            Console.WriteLine($"File deleted: {path}");
        }
        else
        {
            Console.WriteLine($"File not found: {path}");
        }
    }
}

Exists

Exists (string path)

Determines whether the specified file exists.

Parameters

path: The file to check.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string existingFilePath = @"C:\temp\ExistingFile.txt";
        string nonExistingFilePath = @"C:\temp\NonExistentFile.txt";

        // Create a dummy file for testing existence
        File.WriteAllText(existingFilePath, "This file exists.");

        // Check if the file exists.
        bool exists = File.Exists(existingFilePath);
        Console.WriteLine($"Does '{existingFilePath}' exist? {exists}"); // Output: True

        exists = File.Exists(nonExistingFilePath);
        Console.WriteLine($"Does '{nonExistingFilePath}' exist? {exists}"); // Output: False

        // Clean up the dummy file
        if (File.Exists(existingFilePath))
        {
            File.Delete(existingFilePath);
        }
    }
}

ReadAllBytes

ReadAllBytes (string path)

Opens a binary file, reads the contents of the file into a byte array, and then closes the file.

Parameters

path: The file to read.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\BinaryFile.bin";

        // Create a dummy binary file
        byte[] content = { 0x01, 0x02, 0x03, 0x04, 0x05 };
        File.WriteAllBytes(path, content);

        // Read all bytes from the file.
        byte[] fileBytes = File.ReadAllBytes(path);

        Console.WriteLine($"Read {fileBytes.Length} bytes from {path}.");
        foreach (byte b in fileBytes)
        {
            Console.Write($"{b:X2} "); // Print bytes in hex format
        }
        Console.WriteLine();

        // Clean up
        File.Delete(path);
    }
}

ReadAllLines

ReadAllLines (string path)

Opens a text file, reads all lines of the file, and then closes the file.

Parameters

path: The file to read.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\LinesFile.txt";

        // Create a dummy text file with multiple lines
        string[] linesToWrite = { "Line 1", "Line 2", "Line 3" };
        File.WriteAllLines(path, linesToWrite);

        // Read all lines from the file.
        string[] fileLines = File.ReadAllLines(path);

        Console.WriteLine($"Read {fileLines.Length} lines from {path}.");
        foreach (string line in fileLines)
        {
            Console.WriteLine($"- {line}");
        }

        // Clean up
        File.Delete(path);
    }
}

ReadAllText

ReadAllText (string path)

Opens a text file, reads all lines of the file, and then closes the file.

Parameters

path: The file to read.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\TextFile.txt";
        string textToWrite = "This is the entire content of the file.";

        // Create a dummy text file
        File.WriteAllText(path, textToWrite);

        // Read all text from the file.
        string fileContent = File.ReadAllText(path);

        Console.WriteLine($"Read content from {path}:");
        Console.WriteLine(fileContent);

        // Clean up
        File.Delete(path);
    }
}

WriteAllBytes

WriteAllBytes (string path, byte[] bytes)

Creates a new file, writes the specified byte array to the file, and then closes the file. If the target file already exists, it is overwritten.

Parameters

path: The file to write to.
bytes: The bytes to write to the file.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\NewBinaryFile.bin";
        byte[] content = { 0xFF, 0xEE, 0xDD, 0xCC };

        // Write bytes to the file.
        File.WriteAllBytes(path, content);

        Console.WriteLine($"Wrote {content.Length} bytes to {path}");

        // Verify by reading back
        byte[] readBytes = File.ReadAllBytes(path);
        Console.WriteLine($"Read back {readBytes.Length} bytes:");
        foreach (byte b in readBytes)
        {
            Console.Write($"{b:X2} ");
        }
        Console.WriteLine();

        // Clean up
        File.Delete(path);
    }
}

WriteAllLines

WriteAllLines (string path, IEnumerable<string> contents)

Creates a new file, writes a collection of strings to the file, and then closes the file.

Parameters

path: The file to write to.
contents: The lines to write to the file.

using System;
using System.IO;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\NewLinesFile.txt";
        var linesToWrite = new List<string>() { "First line written.", "Second line.", "Third and final." };

        // Write lines to the file.
        File.WriteAllLines(path, linesToWrite);

        Console.WriteLine($"Wrote {linesToWrite.Count} lines to {path}");

        // Verify by reading back
        string[] readLines = File.ReadAllLines(path);
        Console.WriteLine("Content:");
        foreach (string line in readLines)
        {
            Console.WriteLine($"- {line}");
        }

        // Clean up
        File.Delete(path);
    }
}

WriteAllText

WriteAllText (string path, string contents)

Creates a new file, writes the specified string to the file, and then closes the file. If the target file already exists, it is overwritten.

Parameters

path: The file to write to.
contents: The string to write to the file.

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string path = @"C:\temp\NewTextFile.txt";
        string textToWrite = "This is the content that will be written to the new file.";

        // Write text to the file.
        File.WriteAllText(path, textToWrite);

        Console.WriteLine($"Wrote text to {path}");

        // Verify by reading back
        string readText = File.ReadAllText(path);
        Console.WriteLine("Content read back:");
        Console.WriteLine(readText);

        // Clean up
        File.Delete(path);
    }
}

File Class

Methods

See Also

AppendAllLines

Parameters

AppendAllText

Parameters

AppendText

Parameters

Copy

Parameters

Create

Parameters

Delete

Parameters

Exists

Parameters

ReadAllBytes

Parameters

ReadAllLines

Parameters

ReadAllText

Parameters

WriteAllBytes

Parameters

WriteAllLines

Parameters

WriteAllText

Parameters