Question

Could someone help me to convert bittarray to string properly?
I wrote this:

static String BitArrayToStr(BitArray ba)
        {
            byte[] strArr = new byte[ba.Length / 8];

            System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();

            for (int i = 0; i < ba.Length / 8; i++)
            {
                for (int index = i * 8, m = 1; index < i * 8 + 8; index++, m *= 2)
                {
                    strArr[i] += ba.Get(index) ? (byte)m : (byte)0;
                }
            }

            return encoding.GetString(strArr);
        }

but on the output I have this: “���*Ȱ&����L9��q�zȲP���*Ȱ&����L9��q�zȲP���*Ȱ&Y(W�” -many unrecognised symbols, what shoud I do?

Answer 1

Are you sure your input bit array is from a string that was encoded as ASCII?

Using your code I did the following test

string s = "Hello World";
byte[] bytes = Encoding.ASCII.GetBytes(s);
BitArray b = new BitArray(bytes);
string s2 = BitArrayToStr(b);

And s2 came out with the value Hello World as expected.

Update:

As described in the comments, the ASCII Encoder only handles the bytes 32-127 as printable characters, 0-32 which are control characters will display symbols and everything above 127 will use the ASCII fallback to handle the bad bytes.

Here is a quote from MSDN

http://msdn.microsoft.com/en-us/library/system.text.decoderfallback.aspx

A decoding operation can fail if the input byte sequence cannot be mapped by the encoding. For example, an ASCIIEncoding object cannot decode a byte sequence that yields a character having a code point value that is outside the range U+0000 to U+007F.

When an encoding or decoding conversion cannot be performed, the .NET Framework provides a failure-handling mechanism called a fallback. Your application can use predefined .NET Framework encoder and decoder fallbacks, or it can create a custom encoder fallback derived from the EncoderFallback and EncoderFallbackBuffer classes or a custom decoder fallback derived from the DecoderFallback and DecoderFallbackBuffer classes.