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How Do I Read a File As an Array of Bytes in C#

By steve on February 16, 2007.
Updated on January 22, 2012.
Viewed 23,623 times (1 times today).

Article Types	Language Elements	Languages	Technologies
Snippet	IO	C#	.NET

Summary

How do I read a file as an array of bytes?

.NET provides a lot of great tools for reading and writing files, lots of stream classes. If you're like me, I kind of find dealing with streams a pain. If I want to read a file I should only have to say "ReadFile" and the content should be there the way I want.

As a result, I tend to write lots of helper methods that hide the stream manipulations so I don't have to remember them. Here's one that will read any file as an array of bytes. I've found this useful with both binary and text files when I didn't have to analyze the data inside--such as a simple file transfer.

public static byte[] GetBytesFromFile(string fullFilePath)
{
   // this method is limited to 2^32 byte files (4.2 GB)

   FileStream fs = File.OpenRead(fullFilePath);
   try
   {
      byte[] bytes = new byte[fs.Length];
      fs.Read(bytes, 0, Convert.ToInt32(fs.Length));
      fs.Close();
      return bytes;
   }
   finally
   {
      fs.Close();
   }

}

Update

The above is still a good way to read a file using a FileStream object, but a few years on and this functionality is now baked into the .NET framework.

byte[] bytes = File.ReadAllBytes("c:\folder\myfile.ext");

User Comments (3)

Posted 2011 Jun 27 23:28 PM.

For anyone reading this now, there is also File.ReadAllBytes(fullFilePath)

Qu4Z

Posted 2011 Jul 14 07:08 AM.

Note that fs.Close() is called twice on the same object. The first call to Close() could be removed. Also, could dispose of the FileStream in the finally block:

FileStream fs = null;
try
{
fs = File.OpenRead(filePath);
byte[] bytes = new byte[fs.Length];
fs.Read(bytes, 0, Convert.ToInt32(fs.Length));
}
finally
{
if (fs != null)
{
fs.Close();
fs.Dispose();
}
}

Zach D

Posted 2012 Jan 25 03:37 AM.

@Zach D: FileStream is IDisposable, so you could do away with try/finally and have:


using(FileStream fs = File.OpenRead(filePath))
{
  // ...
}

Kawahee

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