Converting string to byte[] creates zero character

Question

In this convert function

public static byte[] GetBytes(string str)
{
    byte[] bytes = new byte[str.Length * sizeof(char)];
    System.Buffer.BlockCopy(str.ToCharArray(), 0, bytes, 0, bytes.Length);
    return bytes;
}

byte[] test = GetBytes("abc");

The resulting array contains zero character

test = [97, 0, 98, 0, 99, 0]

And when we convert byte[] back to string, the result is

string test = "a b c "

How do we make it so it doesn't create those zeroes

Solution 1

First let's look at what your code does wrong. char is 16-bit (2 byte) in .NET framework. Which means when you write sizeof(char), it returns 2. str.Length is 1, so actually your code will be byte[] bytes = new byte[2] is the same byte[2]. So when you use Buffer.BlockCopy() method, you actually copy 2 bytes from a source array to a destination array. Which means your GetBytes() method returns bytes[0] = 32 and bytes[1] = 0 if your string is " ".

Try to use Encoding.ASCII.GetBytes() instead.

When overridden in a derived class, encodes all the characters in the specified string into a sequence of bytes.

const string input = "Soner Gonul";

byte[] array = Encoding.ASCII.GetBytes(input);

foreach ( byte element in array )
{
     Console.WriteLine("{0} = {1}", element, (char)element);
}

Output:

83 = S
111 = o
110 = n
101 = e
114 = r
32 =
71 = G
111 = o
110 = n
117 = u
108 = l

Solution 2

Just to clear the confusion about your answer, char type in C# takes 2 bytes. So, string.toCharArray() returns an array in which each item takes 2 bytes of storage. While copying to byte array where each item takes 1 byte storage, there occurs a data loss. Hence the zeroes showing up in result.
As suggested, Encoding.ASCII.GetBytes is a safer option to use.

Solution 3

In reality .net (at least for 4.0) automatically changes size of char when serialized with BinaryWriter

UTF-8 chars have variable length (might not be 1 byte), ASCII chars have 1 byte

'ē' = 2 bytes

'e' = 1 byte

It must be kept in mind when using

BinaryReader.ReadChars(stream)

In case of word "ēvalds" = 7 bytes size will be different than "evalds" = 6 bytes