File.WriteAllBytes() Method in C# with Examples

File.WriteAllBytes(String) is an inbuilt File class method that is used to create a new file then writes the specified byte array to the file and then closes the file. If the target file already exists, it is overwritten.

Syntax:

public static void WriteAllBytes (string path, byte[] bytes);

Parameter: This function accepts two parameters which are illustrated below: 

• path: This is the specified file where the byte array is going to be written.
• bytes: This is the specified bytes that are going to be written into the file.

Exceptions:

• ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
• ArgumentNullException: The path is null or the byte array is empty.
• PathTooLongException: The specified path, file name, or both exceed the system-defined maximum length.
• DirectoryNotFoundException: The specified path is invalid.
• IOException: An I/O error occurred while opening the file.
• UnauthorizedAccessException: The path specified a file that is read-only. OR the path specified a file that is hidden. OR this operation is not supported on the current platform. OR the path specified a directory. OR the caller does not have the required permission.
• NotSupportedException: The path is in an invalid format.
• SecurityException: The caller does not have the required permission.

Below are the programs to illustrate the File.WriteAllBytes(String, Byte[]) method.
Program 1: Initially, no file was created. Below code, itself creates a file file.txt and writes some specified byte array and then finally close the file.

CSharp

// C# program to illustrate the usage
// of File.WriteAllBytes() method

// Using System, System.IO
// and System.Text namespaces
using System;
using System.IO;
using System.Text;

class GFG {
    static void Main(string[] args)
    {
        // Specifying a file name
        var path = @"file.txt";

        // Specifying a byte array
        string text = "GFG is a CS portal.";
        byte[] data = Encoding.ASCII.GetBytes(text);

        // Calling the WriteAllBytes() function
        // to write specified byte array to the file
        File.WriteAllBytes(path, data);
        Console.WriteLine("The data has been written to the file.");
    }
}

Output:

The data has been written to the file.

Above code gives the output as shown above and creates a file with some specified contents shown below-

Program 2: Initially, a file was created with some contents shown below:

Below code, overwrites the above file contents with a specified byte array data.

CSharp

// C# program to illustrate the usage
// of File.WriteAllBytes() method

// Using System, System.IO
// and System.Text namespaces
using System;
using System.IO;
using System.Text;

class GFG {
    static void Main(string[] args)
    {
        // Specifying a file name
        var path = @"file.txt";

        // Specifying a byte array data
        string text = "GeeksforGeeks";
        byte[] data = Encoding.ASCII.GetBytes(text);

        // Calling the WriteAllBytes() function
        // to overwrite the file contents with the
        // specified byte array data
        File.WriteAllBytes(path, data);
        Console.WriteLine("The data has been overwritten to the file.");
    }
}

Output:

The data has been overwritten to the file.

After running above code, the above output is shown and the file contents get overwritten which is shown below-