Getting values in C# from a COM Event sending an array of strings as a variant

[MikalE]

I’m using a third-party ActicveX component that has the following description for one of its events:

OnAlarm(CallNumber as BSTR,
AlarmType as atAlarmType,
NumberOfLocations as long,
LocationIdentity(NumberOfLocations) as array of VARIANT containing BSTR,
LocationType(NumberOfLocations) as array of VARIANT containing atlocationType,
LocationTime(NumberOfLocations) as arrey of VARIANT containing BSTR)

They mean by this that LocationType is an array of VARIANTS (containing enumeration)

When the OnAlarm Event is raised I have problems getting the 3 last values from it.

I have ported my application from VB.Net to C# and this is the only problem I can’t figure out how to solve in doing so.
In VB.Net it’s very easy to access these values as long as you don’t have the strong typing feature enabled. But not in C# where VARIANT type does not exist and is rather referenced as an object.

This is how OnAlarm looks in C#:

void OnAlarm(string CallNumber, ATOAC2Lib.atAlarmType AlarmType, int NumberOfLocations, ref object LocationIdentity, ref object LocationType, ref object LocationTime)
    Member of ATOAC2Lib._IatAlarm3Events

In VB.Net the code I was using looked like this:

 Private Sub atAlarm2_OnAlarm1(ByVal CallNumber As String, ByVal AlarmType As ATOAC2Lib.atAlarmType, ByVal NumberOfLocations As Integer, ByRef LocationIdentity As Object, ByRef LocationType As Object, ByRef LocationTime As Object) Handles atAlarm2.OnAlarm
 
        Dim ret, i As Integer
        Dim SecondLocationTime, FirstLocationTime, SecondLocation, FirstLocation, s As String
 
        Try
            If AlarmType <> ATOAC2Lib.atAlarmType.atAlarmType_Test Then
                FirstLocationTime = "0"
                SecondLocationTime = "0"
                SecondLocation = "0"
                FirstLocation = "0"
 
                For i = 0 To NumberOfLocations - 1 
                    If i = 0 Then
                        If LocationType(i) = ATOAC2Lib.atLocationType.atLocationType_System900_Locator Then
                            FirstLocation = HexToDec(LocationIdentity(i))
                            FirstLocationTime = LocationTime(i)
                        End If
                    ElseIf i = 1 Then
                        mylogfile.writelog(3, "AL2-" & LocationIdentity(i))
                        If LocationType(i) = ATOAC2Lib.atLocationType.atLocationType_System900_Locator Then
                            SecondLocation = HexToDec(LocationIdentity(i))
                            SecondLocationTime = LocationTime(i)
                        End If
                    End If
                Next i
Etc.
 

This is how the same method looks in C# after I converted it:

 private void atAlarm2_OnAlarm1(string CallNumber, ATOAC2Lib.atAlarmType AlarmType, int NumberOfLocations, ref object LocationIdentity, ref object LocationType, ref object LocationTime)
        {
            int i;
            string SecondLocationTime;
            string FirstLocationTime;
            string SecondLocation;
            string FirstLocation;
 
            String[] tempLocationIdentity;
            ATOAC2Lib.atLocationType[] tempLocationType;
            String[] tempLocationTime;
 
            try
            {
                logger.Debug("Event atAlarm2_OnAlarm1 raised");
 
                tempLocationIdentity = (String[])LocationIdentity;
                tempLocationType = (ATOAC2Lib.atLocationType[])LocationType;
                tempLocationTime = (String[])LocationTime;
 
                if (AlarmType != ATOAC2Lib.atAlarmType.atAlarmType_Test)
                {
                    FirstLocationTime = "0";
                    SecondLocationTime = "0";
                    SecondLocation = "0";
                    FirstLocation = "0";
                    AL_MsgCounter++;
                    UpdateLabelText(this.LabelALCount, AL_MsgCounter.ToString());
 
                    // Extract First/Second Location and First/Second Time
                    for (i = 0; i <= NumberOfLocations - 1; i++)
                    {
                        if (i == 0)
                        {
                            logger.Debug("First alarm location at " + tempLocationIdentity[i]);
                            //mylogfile.WriteLog(3, "AL1-" + tempLocationIdentity[i]);
                            if (tempLocationType[i] == ATOAC2Lib.atLocationType.atLocationType_System900_Locator)
                            {
                                FirstLocation = HexToDec(tempLocationIdentity[i]);
                                FirstLocationTime = tempLocationTime[i];
                            }
                        }
                        else if (i == 1)
                        {
                            logger.Debug("Second alarm location at " + tempLocationIdentity[i]);
                            //mylogfile.WriteLog(3, "AL2-" + tempLocationIdentity[i]);
                            if (tempLocationType[i] == ATOAC2Lib.atLocationType.atLocationType_System900_Locator)
                            {
                                SecondLocation = HexToDec(tempLocationIdentity[i]);
                                SecondLocationTime = tempLocationTime[i];
                            }
                        }
                    }
Etc.

This code compiles with no problem, but running the application returns the following exception:

System.InvalidCastException: Unable to cast object of type ‘System.Object[]’ to type ‘System.String[]’.

Anyone that knows how to solve this?
I'm very thankful for all feedback.