StreamReader vs BinaryReader?

Question

Both StreamReader and BinaryReader can be used to get data from binary file ( for example )

BinaryReader :

   using (FileStream fs = File.Open(@"c:\1.bin",FileMode.Open))
            {
                    byte[] data = new BinaryReader(fs).ReadBytes((int)fs.Length);
                    Encoding.getstring....
            }

StreamReader :

  using (FileStream fs = File.Open(@"c:\1.bin",FileMode.Open))
            {
                using (StreamReader sr = new StreamReader(fs,Encoding.UTF8))
                {
                       var myString=sr.ReadToEnd();
                }
            }

What is the difference and when should I use which ?

One is suitable for text files, the other for binary files? As you even elude to in your sample code. — Adam Houldsworth
– Adam Houldsworth, Commented Apr 27, 2012 at 15:58
Yes, but presumably encoded as a UTF-8 string... so in essence would be text. — Adam Houldsworth
– Adam Houldsworth, Commented Apr 27, 2012 at 16:02
@RoyiNamir "utf8 string can contain binary data" - what do you consider "binary data" ? — Henk Holterman
– Henk Holterman, Commented Apr 27, 2012 at 16:08

Jon Skeet · Accepted Answer · 2012-04-27 15:59:29Z

85

Both StreamReader and BinaryReader can be used to get data from binary file

Well, StreamReader can be used to get text data from a binary representation of text.

BinaryReader can be used to get arbitrary binary data. If some of that binary data happens to be a representation of text, that's fine - but it doesn't have to be.

Bottom line:

If the entirety of your data is a straightforward binary encoding of text data, use StreamReader.
If you've fundamentally got binary data which may happen to have some portions in text, use BinaryReader

So for example, you wouldn't try to read a JPEG file with StreamReader.

answered Apr 27, 2012 at 15:59

Jon Skeet

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12 Comments

Jon Skeet Over a year ago

@RoyiNamir: No, a string is text. There's not even such a thing as a "UTF-8 string" - there's a UTF-8 binary representation of a string... A string holds text data - it's a sequence of characters. You then convert that to a binary representation using an encoding, such as UTF-8. Please read csharpindepth.com/Articles/General/Unicode.aspx

Jon Skeet Over a year ago

@Nudier: No, neither StreamReader nor BinaryReader derive from Stream. There is absolutely a huge difference between using StreamReader and using BinaryReader.

Jon Skeet Over a year ago

@RoyiNamir: "Binary character" is a contradiction in terms. It's like talking about a "floating point integer". You must not read arbitrary binary data (e.g. a JPEG file) as text. You will lose information.

Jon Skeet Over a year ago

@RoyiNamir: Are you converting it into text in a naive way in both cases? If so, you're probably losing data in both cases, possibly consistently. Just don't do it - binary data isn't text, so don't try to pretend it is. If you really need to represent arbitrary binary data in text, use base64.

Jon Skeet Over a year ago

@RoyiNamir: Unicode can represent almost any character you care to mention. But the key word here is character - not byte. Characters are for text. If you haven't got text, you haven't got characters.

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