How do I concatenate 2 bytes?

Question

I have 2 bytes:

byte b1 = 0x5a;  
byte b2 = 0x25;

How do I get 0x5a25 ?

Answer 1

The simplest would be

b1*256 + b2

Answer 2

Using bit operators: (b1 << 8) | b2 or just as effective (b1 << 8) + b2

Answer 3

byte b1 = 0x5a;
byte b2 = 0x25;

Int16 x=0;

x= b1;
x= x << 8;
x +=b2;

Answer 4

It can be done using bitwise operators '<<' and '|'

public int Combine(byte b1, byte b2)
{
    int combined = b1 << 8 | b2;
    return combined;
}

Usage example:

[Test]
public void Test()
{
    byte b1 = 0x5a;
    byte b2 = 0x25;
    var combine = Combine(b1, b2);
    Assert.That(combine, Is.EqualTo(0x5a25));
}

Answer 5

A more explicit solution (also one that might be easier to understand and extend to byte to int i.e.):

using System.Runtime.InteropServices;
[StructLayout(LayoutKind.Explicit)]
struct Byte2Short {
  [FieldOffset(0)]
  public byte lowerByte;
  [FieldOffset(1)]
  public byte higherByte;
  [FieldOffset(0)]
  public short Short;
}

Usage:

var result = (new Byte2Short(){lowerByte = b1, higherByte = b2}).Short;

This lets the compiler do all the bit-fiddling and since Byte2Short is a struct, not a class, the new does not even allocate a new heap object ;)