.NET BinaryReader not obeying encoding

Question

When reading in a Binary file using System.IO.BinaryReader the byte order seems to be unaffected when using any of the multi-byte Read methods.

BinaryReader br = new BinaryReader(fs, System.Text.Encoding.BigEndianUnicode);

and

BinaryReader br = new BinaryReader(fs, System.Text.Encoding.Unicode);

are producing the same results for me.

This is causing me a lot of frustration because I have to reverse the byte order constantly while reading in data structures.

Screenshot - Big Endian Unicode

Screenshot - Little Endian Unicode

I've tested this on .NET 3 through 4.5

I assume the BinaryRead only works on textfiles, but from the chunks in your code the file seems to be binary. Then as far as I know you have to handcode it using the Convert class — Mario The Spoon
– Mario The Spoon, Commented Oct 16, 2012 at 4:51
What is the result if you specify encoding for the reader as well? — larsmoa
– larsmoa, Commented Oct 16, 2012 at 5:01

Marc Gravell · Accepted Answer · 2012-10-16 05:20:51Z

8

BinaryReader only uses the Encoding when handling string data (pretty much, just ReadString()). ReadBytes etc do not involve Encoding - it just reads the binary data. Since you only call ReadBytes, this (Encoding) never gets a look-in.

If the data is out-of-order, then it sounds like the file wasn't created with BinaryWriter. If it wasn't created with BinaryWriter then BinaryReader probably isn't all that useful - you could just use Stream.

answered Oct 16, 2012 at 5:20

Marc Gravell

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1 Comment

Jon Skeet Over a year ago

A BinaryReader-like class can still be useful if you know the format - but if you need to switch endianness, EndianBinaryReader is what you want, from MiscUtil :)

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