C# Signature:

[DllImport("Netapi32.dll")]
extern static int NetLocalGroupEnum([MarshalAs(UnmanagedType.LPWStr)]
       string servername,
       int level,
       out IntPtr bufptr,
       int prefmaxlen,
       out int entriesread,
       out int totalentries,
       ref int resume_handle);

VB Signature:

Declare Function NetLocalGroupEnum Lib "netapi32.dll" (TODO) As TODO

User-Defined Types:

Managed version of the LOCALGROUP_INFO_1 structure:

[StructLayout(LayoutKind.Sequential)]
private struct GroupInfo
{
    [MarshalAs(UnmanagedType.LPWStr)] public string name;
    [MarshalAs(UnmanagedType.LPWStr)] public string comment;
}

Notes:

None.

Tips & Tricks:

Largest challenge is marshalling the pointer to the array of structures which the output is placed in.

In this example, I use a do/while which doubles the size of the buffer until it is large enough to contain all of the groups that are on the server. The API call is designed so that you can read sequentially (ERROR_MORE_DATA), but I didn't want to deal with marshalling returned data stored in more than one of the pointers to the array of structures which the output is placed in!

Sample Code:

int    size        =1024;    //Start with 1k
IntPtr    bufptr        =new IntPtr(size);
int    level        =1;
int    prefmaxlen    =1023;
int    entriesread    =0;
int    totalentries    =0;
int    resume_handle    =0;
int    err        =0;
do
{
    switch(err=NetLocalGroupEnum(
                    m_Server,
                    level,
                    out bufptr,
                    prefmaxlen,
                    out entriesread,
                    out totalentries,
                    ref resume_handle
                ))
    {
        //If there is more data, double the size of the buffer...
        case 2123    :        //NERR_BufTooSmall    
        case 234    :        //ERROR_MORE_DATA    
            size*=2;
            bufptr=new IntPtr(size);
            prefmaxlen=size-1;    //Increase the size you want read as well
            resume_handle=0;    //And reset the resume_handle or you'll just pick up where you left off.

            break;
        case 2351    :        //NERR_InvalidComputer    
        //case 2123    :    //ERROR_ACCESS_DENIED    
        case 0    :        //NERR_Success    
        default    :    break;
    }
}
while(err==234);    // and start over

GroupInfo[] group=new GroupInfo(totalentries); //See user type above

IntPtr iter = bufptr;

for(int i=0; i < totalentries; i++)
{
    group[totalentries] = (GroupInfo)Marshal.PtrToStructure(iter, typeof(GroupInfo));
    iter = (IntPtr)((int)iter + Marshal.SizeOf(typeof(GroupInfo)));
}

Alternative Managed API:

Do you know one? Please contribute it!