Convert from BitArray to Byte

Question

I have a BitArray with the length of 8, and I need a function to convert it to a byte. How to do it?

Specifically, I need a correct function of ConvertToByte:

BitArray bit = new BitArray(new bool[]
{
    false, false, false, false,
    false, false, false, true
});

//How to write ConvertToByte
byte myByte = ConvertToByte(bit);
var recoveredBit = new BitArray(new[] { myByte });
Assert.AreEqual(bit, recoveredBit);

Answer 1

This should work:

byte ConvertToByte(BitArray bits)
{
    if (bits.Count != 8)
    {
        throw new ArgumentException("bits");
    }
    byte[] bytes = new byte[1];
    bits.CopyTo(bytes, 0);
    return bytes[0];
}

Answer 2

A bit late post, but this works for me:

public static byte[] BitArrayToByteArray(BitArray bits)
{
    byte[] ret = new byte[(bits.Length - 1) / 8 + 1];
    bits.CopyTo(ret, 0);
    return ret;
}

Works with:

string text = "Test";
byte[] bytes = System.Text.Encoding.ASCII.GetBytes(text);
BitArray bits = new BitArray(bytes);
bytes[] bytesBack = BitArrayToByteArray(bits);
string textBack = System.Text.Encoding.ASCII.GetString(bytesBack);
// bytes == bytesBack
// text = textBack

.

Answer 3

A poor man's solution:

protected byte ConvertToByte(BitArray bits)
{
    if (bits.Count != 8)
    {
        throw new ArgumentException("illegal number of bits");
    }

    byte b = 0;
    if (bits.Get(7)) b++;
    if (bits.Get(6)) b += 2;
    if (bits.Get(5)) b += 4;
    if (bits.Get(4)) b += 8;
    if (bits.Get(3)) b += 16;
    if (bits.Get(2)) b += 32;
    if (bits.Get(1)) b += 64;
    if (bits.Get(0)) b += 128;
    return b;
}

Answer 4

This should do the trick. However the previous answer is quite likely the better option.

    public byte ConvertToByte(BitArray bits)
    {
        if (bits.Count > 8)
            throw new ArgumentException("ConvertToByte can only work with a BitArray containing a maximum of 8 values");

        byte result = 0;

        for (byte i = 0; i < bits.Count; i++)
        {
            if (bits[i])
                result |= (byte)(1 << i);
        }

        return result;
    }

In the example you posted the resulting byte will be 0x80. In other words the first value in the BitArray coresponds to the first bit in the returned byte.