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, Apr 27 '12 at 15:58
Yes, but presumably encoded as a UTF-8 string... so in essence would be text. — Adam Houldsworth, Apr 27 '12 at 16:02
@RoyiNamir "utf8 string can contain binary data" - what do you consider "binary data" ? — H H, Apr 27 '12 at 16:08
@HenkHolterman for eaxmple : view jpeg content in total commander — Royi Namir, Apr 27 '12 at 16:11
@RoyiNamir - you mean control chars and bytes outside the ASCII range? — H H, Apr 27 '12 at 16:13
@Adam Houldsworth: Both streams & byte arrays can hold binary data. Binary files can also be read/written via disk or even via network sockets with either method. See `GetStreamAsync` & `GetByteArrayAsync` methods of `System.Net.Http.Httpclient` as an example. — Zimba, Nov 19 '19 at 14:01

score 84 · Accepted Answer · answered Apr 27 '12 at 15:59

84

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 '12 at 15:59

Jon Skeet

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but a utf8 string can contains inside it even binary data.. so... ? – Royi Namir Apr 27 '12 at 16:01
isnt a utf8 string can hold any info ? – Royi Namir Apr 27 '12 at 16:04
4

@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 http://csharpindepth.com/Articles/General/Unicode.aspx – Jon Skeet Apr 27 '12 at 16:04
as you may know they all inherits from the base class stream, so there is no difference to use one of those. – Nudier Mena Apr 27 '12 at 16:05
@jon what im saying is that there isnt a binary charcter which i cant save it in string... so i can get the bin content to string via StreamReader and BinaryReader – Royi Namir Apr 27 '12 at 16:06
1

@Nudier: No, neither StreamReader nor BinaryReader derive from Stream. There is *absolutely* a huge difference between using StreamReader and using BinaryReader. – Jon Skeet Apr 27 '12 at 16:06
6

@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 Apr 27 '12 at 16:07
@jon ok ... one final thing : ive just read a jpeg file using binary reader -byte array size was 740. than i read via streamreader - to a string - string .length was still 740.... so...? – Royi Namir Apr 27 '12 at 16:10
1

@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 Apr 27 '12 at 16:12
@JonSkeet i got my problem. unicode is only for text. i thought it could also represent some ugly charcters . this was the source of my mistake. thanks. – Royi Namir Apr 27 '12 at 16:29
2

@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. – Jon Skeet Apr 27 '12 at 16:31
@giorgim: Well that's why you can lose data. And fundamentally it's just a bad idea to treat data of one form as another - it encourages you to perform all kinds of inappropriate operations on it. – Jon Skeet Dec 10 '14 at 09:24

StreamReader vs BinaryReader?

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