How do you convert multistring to/from C# string collection?

Question

Multistrings (double null-terminated string of null-separated strings) are common in the Windows API. What\'s a good method for converting a multistring returned from an API

Answer 1

I've tested the StringArrayToMultiString method, using the ChangeServiceConfig() function to change the dependencies of a Windows service, and it works nicely for zero, one and many strings.

In the meantime, I've worked out a solution for decoding a multistring received from an API call. For example, the SCardListReaders() function returns a multistring of PC/SC reader names. I declared this as:

[DllImport("winscard.dll", CharSet = CharSet.Auto)]
static extern int SCardListReaders(
    IntPtr context,
    string groups,
    char[] readers,
    ref uint readersLen
    );

Note that the readers parameter, which returns the multistring, is declared as char[]. The return value is easily parsed and converted into a collection of strings:

static string[] MultiStringToArray(
    char[] multistring
    )
{
    List stringList = new List();
    int i = 0;
    while (i < multistring.Length)
    {
        int j = i;
        if (multistring[j++] == '\0') break;
        while (j < multistring.Length)
        {
            if (multistring[j++] == '\0')
            {
                stringList.Add(new string(multistring, i, j - i - 1));
                i = j;
                break;
            }
        }
    }

    return stringList.ToArray();
}