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File.ReadAllBytes() Method in C# with Examples

  • Last Updated : 09 Mar, 2021

File.ReadAllBytes(String) is an inbuilt File class method that is used to open a specified or created binary file and then reads the contents of the file into a byte array and then closes the file.
Syntax: 
 

public static byte[] ReadAllBytes (string path);

Parameter: This function accepts a parameter which is illustrated below: 
 

  • path: This is the specified file to open for reading.

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.
  • 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: This operation is not supported on the current platform. OR the path specified a directory. OR the caller does not have the required permission.
  • FileNotFoundException: The file specified in the path was not found.
  • NotSupportedException: The path is in an invalid format.
  • SecurityException: The caller does not have the required permission.

Return Value: Returns a byte array containing the contents of the file.
Below are the programs to illustrate the File.ReadAllBytes(String) method.
Program 1: Initially, a file file.txt is created with some contents shown below-
 

file.txt



 

C#




// C# program to illustrate the usage
// of File.ReadAllBytes(String) method
  
// Using System and System.IO namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifying a file
        string path = @"file.txt";
  
        // Calling the ReadAllBytes() function
        byte[] readText = File.ReadAllBytes(path);
        foreach(byte s in readText)
        {
            // Printing the binary array value of
            // the file contents
            Console.WriteLine(s);
        }
    }
}

Output: 
 

53

Program 2: Initially, no file was created. Below code itself create a file file.txt with some specified contents.
 

C#




// C# program to illustrate the usage
// of File.ReadAllBytes(String) method
  
// Using System and System.IO namespaces
using System;
using System.IO;
  
class GFG {
    public static void Main()
    {
        // Specifying a file
        string path = @"file.txt";
  
        // Adding below contents to the file
        string[] createText = { "GFG" };
        File.WriteAllLines(path, createText);
  
        // Calling the ReadAllBytes() function
        byte[] readText = File.ReadAllBytes(path);
        foreach(byte s in readText)
        {
            // Printing the binary array value of
            // the file contents
            Console.WriteLine(s);
        }
    }
}

Output: 
 

71
70
71
10



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