How to get a null terminated string from a C# string?

Question

• I am communicating with a server who needs null terminated string
• How can I do this smartly in C#?

Answer 1

I assume you're implementing some kind of binary protocol, if the strings are null terminated. Are you using a BinaryWriter?

The default BinaryWriter writes strings as length prefixed. You can change that behavior:

class MyBinaryWriter : BinaryWriter
{
    private Encoding _encoding = Encoding.Default;

    public override void Write(string value)
    {
        byte[] buffer = _encoding.GetBytes(value);
        Write(buffer);
        Write((byte)0);
    }
}

Then you can just write any string like this:

using (MyBinaryWriter writer = new MyBinaryWriter(myStream))
{
    writer.Write("Some string");
}

You may need to adjust the _encoding bit, depending on your needs.

You can of course expand the class with specific needs for other data types you might need to transfer, keeping your actual protocol implementation nice and clean. You'll probably also need your own (very similar) BinaryReader.

Answer 2

I think the smart way is to do it simply.

string str = "An example string" + char.MinValue; // Add null terminator.

Then convert it into bytes to send to the server.

byte[] buffer = ASCIIEncoding.ASCII.GetBytes(str);

Of course what encoding you use depends on what encoding the server expects.

Answer 3

The strings are already null terminated. Although the string itself doesn't contain a null character, a null character always follows the string in memory.

However, strings in .NET are unicode, so they are stored as UTF-16/UCS-2 in memory, and the server might expect a different encoding, usually an 8 bit encoding. Then you would have to encode the string into a byte array and place a zero byte at the end:

byte[] data = Encoding.Default.GetBytes(theString);
byte[] zdata = new byte[data.Length + 1];
data.CopyTo(zdata, 0);

(The zdata array is all filled with zeroes when creates, so you don't have to actually set the extra byte to zero.)

Answer 4

You add a null character to the end of the string. .NET strings can contain null characters.