FileInfo - ReadAllBytes

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

Try it

public static string FileName = "test.txt";

public static void Main()
{
	SaveFile();
	
	// C# Extension Method: FileInfo - ReadAllBytes
	var bytes = FileName.ToFileInfo().ReadAllBytes();
	
	Console.WriteLine(System.Text.Encoding.Default.GetString(bytes));
}

private static void SaveFile()
{
	var html =
    @"<!DOCTYPE html>
<html>
<body>
<h1>This is <b>bold</b> heading</h1>
<p>This is <u>underlined</u> paragraph</p>
<h2>This is <i>italic</i> heading</h2>
</body>
</html> ";
	
	html.SaveAs(FileName);
}

View Source 
using System;
using System.IO;

public static partial class Extensions
{
    /// <summary>
    ///     Opens a binary file, reads the contents of the file into a byte array, and then closes the file.
    /// </summary>
    /// <param name="this">The file to open for reading.</param>
    /// <returns>A byte array containing the contents of the file.</returns>
    /// ###
    /// <exception cref="T:System.ArgumentException">
    ///     <paramref name="this" /> is a zero-length string, contains only
    ///     white space, or contains one or more invalid characters as defined by
    ///     <see
    ///         cref="F:System.IO.Path.InvalidPathChars" />
    ///     .
    /// </exception>
    /// ###
    /// <exception cref="T:System.ArgumentNullException">
    ///     <paramref name="this" /> is null.
    /// </exception>
    /// ###
    /// <exception cref="T:System.IO.PathTooLongException">
    ///     The specified @this, 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.
    /// </exception>
    /// ###
    /// <exception cref="T:System.IO.DirectoryNotFoundException">
    ///     The specified @this is invalid (for example, it is on
    ///     an unmapped drive).
    /// </exception>
    /// ###
    /// <exception cref="T:System.IO.IOException">An I/O error occurred while opening the file.</exception>
    /// ###
    /// <exception cref="T:System.UnauthorizedAccessException">
    ///     This operation is not supported on the current
    ///     platform.-or- <paramref name="this" /> specified a directory.-or- The caller does not have the required
    ///     permission.
    /// </exception>
    /// ###
    /// <exception cref="T:System.IO.FileNotFoundException">
    ///     The file specified in <paramref name="this" /> was not
    ///     found.
    /// </exception>
    /// ###
    /// <exception cref="T:System.NotSupportedException">
    ///     <paramref name="this" /> is in an invalid format.
    /// </exception>
    /// ###
    /// <exception cref="T:System.Security.SecurityException">The caller does not have the required permission.</exception>
    public static Byte[] ReadAllBytes(this FileInfo @this)
    {
        return File.ReadAllBytes(@this.FullName);
    }
}