BitConverter.ToInt16 doesn't work correct

[=?Utf-8?B?U3VzaGlTZWFu?=]

Hello. I have a problem with getting short value from 2 byte array.
I have this code. There are 2 short values in bytes.

byte[] cast = { 18, 152, 00, 80 };
Int32 port = BitConverter.ToInt16(cast, 0); // -26606 - wrong!
Int32 port2 = BitConverter.ToInt16(cast, 2); // 20480 - wrong!

//port and port2 get not correct values
//and I found solution in google
short result1 = (short)(((short)cast[1]) | (short)(cast[0] * 256)); //4760 -
correct!
short result2 = (short)(((short)cast[3]) | (short)(cast[2] * 256)); //80 -
correct!

why it happends? How make BitConverter work correct?

[=?Utf-8?B?U3VzaGlTZWFu?=]

"Peter Duniho" wrote:

Don't lie to it about the data you're passing it. If you want it to
convert data that you have that starts in big-endian format, you need to
convert that data to little-endian before you pass it to BitConverter

How to make this convert to little-endian?

[Marc Gravell]

Note that Jon Skeet has an EndianBitConverter (below) which may be of
use:

http://www.yoda.arachsys.com/csharp/miscutil/

Marc

[Michael C]

"SushiSean" <Su*******@discussions.microsoft.comwrote in message
news:12**********************************@microsof t.com...

Hello. I have a problem with getting short value from 2 byte array.
I have this code. There are 2 short values in bytes.

byte[] cast = { 18, 152, 00, 80 };
Int32 port = BitConverter.ToInt16(cast, 0); // -26606 - wrong!
Int32 port2 = BitConverter.ToInt16(cast, 2); // 20480 - wrong!

//port and port2 get not correct values
//and I found solution in google
short result1 = (short)(((short)cast[1]) | (short)(cast[0] * 256));
//4760 -
correct!
short result2 = (short)(((short)cast[3]) | (short)(cast[2] * 256)); //80 -
correct!

why it happends? How make BitConverter work correct?

You could just do cast[0] * 256 + cast[1]. You will need to work out how to
handle values of 128 or above for the first byte.

[Marc Gravell]

Note that this will only work if the binary data is a single value
(however many bytes that is for the type in question); if it is a true
stream of successive values you could be in a pickle.

Minor aside; personally I would have called reader.ReadBytes() to fill
the buffer in either case, and then (if littleEndian) reversed the
buffer locally. Horses for courses...

Marc

[Marc Gravell]

That should probably be a bitwise "or" (|), not a logical "or" (||).
And again, it only helps with a few cases (single, simple values like
short). IMO, the better solution is to leave the byte-stream alone,
and use EndianBitConverter. This will work for multiple sequenced
values, and all data types.

Marc