I finally got this sorted out myself a couple days ago. There are two parts, one to check the registry and another to check the vid/pid of the device.
The registry method I use just to make sure I don't capture a null modem emulator like com0com.
/// <summary>
/// Removes any comm ports that are not explicitly defined as allowed in ALLOWED_TYPES
/// </summary>
/// <param name="allPorts">reference to List that will be checked</param>
/// <returns></returns>
private static void nullModemCheck(ref List<string> allPorts)
{
// Open registry to get the COM Ports available with the system
RegistryKey regKey = Registry.LocalMachine;
// Defined as: private const string REG_COM_STRING ="HARDWAREDEVICEMAPSERIALCOMM";
regKey = regKey.OpenSubKey(REG_COM_STRING);
Dictionary<string, string> tempDict = new Dictionary<string, string>();
foreach (string p in allPorts)
tempDict.Add(p, p);
// This holds any matches we may find
string match = "";
foreach (string subKey in regKey.GetValueNames())
{
// Name must contain either VCP or Seial to be valid. Process any entries NOT matching
// Compare to subKey (name of RegKey entry)
if (!(subKey.Contains("Serial") || subKey.Contains("VCP")))
{
// Okay, this might be an illegal port.
// Peek in the dictionary, do we have this key? Compare to regKey.GetValue(subKey)
if(tempDict.TryGetValue(regKey.GetValue(subKey).ToString(), out match))
{
// Kill it!
allPorts.Remove(match);
// Reset our output string
match = "";
}
}
}
regKey.Close();
}
The vid/pid portion was gleaned from techinpro
/// <summary>
/// Compile an array of COM port names associated with given VID and PID
/// </summary>
/// <param name="VID">string representing the vendor id of the USB/Serial convertor</param>
/// <param name="PID">string representing the product id of the USB/Serial convertor</param>
/// <returns></returns>
private static List<string> getPortByVPid(String VID, String PID)
{
String pattern = String.Format("^VID_{0}.PID_{1}", VID, PID);
Regex _rx = new Regex(pattern, RegexOptions.IgnoreCase);
List<string> comports = new List<string>();
RegistryKey rk1 = Registry.LocalMachine;
RegistryKey rk2 = rk1.OpenSubKey("SYSTEM\CurrentControlSet\Enum");
foreach (String s3 in rk2.GetSubKeyNames())
{
RegistryKey rk3 = rk2.OpenSubKey(s3);
foreach (String s in rk3.GetSubKeyNames())
{
if (_rx.Match(s).Success)
{
RegistryKey rk4 = rk3.OpenSubKey(s);
foreach (String s2 in rk4.GetSubKeyNames())
{
RegistryKey rk5 = rk4.OpenSubKey(s2);
RegistryKey rk6 = rk5.OpenSubKey("Device Parameters");
comports.Add((string)rk6.GetValue("PortName"));
}
}
}
}
return comports;
}
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