Answer and Hangup a call using TAPI3 C#

Question

I'm stuck in TAPI programming. I've created a program to monitor activity of phone call. Everything is working fine, but now I want to implement a functionality to accept and reject a call from web directly.

what I've done is below:

namespace Shared
{
    public partial class Site : System.Web.UI.MasterPage
    {
        public static ITAddress ln;
        static int index = -1;
        static int line;
        static ITAddress[] ia;
        protected void Page_Load(object sender, EventArgs e)
        {
            #region TAPI
            TAPIClass tobj;
            int[] registertoken;
            tobj = new TAPI3Lib.TAPIClass();
            tobj.Initialize();

            IEnumAddress ea = tobj.EnumerateAddresses();

            uint lines;


            uint arg3 = 0;
            int TotalLines = 0;
            lines = 0;
            foreach (TAPI3Lib.ITAddress ad in (tobj.Addresses as TAPI3Lib.ITCollection))
            {
                TotalLines++;
            }

            callnotification cn = new callnotification();
            tobj.ITTAPIEventNotification_Event_Event += new TAPI3Lib.ITTAPIEventNotification_EventEventHandler(cn.Event);
            tobj.EventFilter = (int)(TAPI_EVENT.TE_CALLNOTIFICATION |
                TAPI_EVENT.TE_DIGITEVENT |
                TAPI_EVENT.TE_PHONEEVENT |
                TAPI_EVENT.TE_CALLSTATE |
                TAPI_EVENT.TE_GENERATEEVENT |
                TAPI_EVENT.TE_GATHERDIGITS |
                TAPI_EVENT.TE_REQUEST);


            registertoken = new int[TotalLines];
            ia = new TAPI3Lib.ITAddress[TotalLines];
            for (int i = 0; i = 0)
                                    {
                                        ln = ia[line];
                                    }
                                    IEnumCall ec = ln.EnumerateCalls();
                                    uint arg = 0;
                                    ITCallInfo ici;
                                    try
                                    {
                                        ec.Next(1, out ici, ref arg);
                                        ITBasicCallControl2 bc = (TAPI3Lib.ITBasicCallControl2)ici;
                                        if (ici != null && ici.CallState == CALL_STATE.CS_OFFERING)
                                        {
                                            if (bc != null)
                                            {
                                                bc.Answer();
                                            }
                                        }
                                    }
                                    catch (Exception ex)
                                    {
                                        COMException comEx = ex as COMException;
                                        if (comEx != null)
                                            comEx.ErrorCode.ToString();
                                        else
                                        {
                                            string aa = ex.Message;
                                        }
                                    }

                                    //addtolist("Call Offering from " + callernumber + " to Ext " + viaextension + " via DID " + DIDNumber);
                                    break;
                                case TAPI3Lib.CALL_STATE.CS_IDLE:
                                    //addtolist("Call is created!");
                                    break;
                            }
                            break;
                    }
                }
                catch (Exception ex)
                {
                    //MessageBox.Show(ex.StackTrace.ToString());
                }
            }
        }
        #endregion
    }
}

I'm always getting ITBasicCallControl2 bc NULL and when I press the Accept button, nothing happens.

Answer 1

Okay, so the first thing you have to do in order to successfully answer calls, is to register your line with owner rights.

tobj.RegisterCallNotifications(ln, true, true, TapiConstants.TAPIMEDIATYPE_AUDIO, 2);

After that, you can either iterate through every call using EnumerateCalls(), or you can implement the ITTAPIEventNotification interface to get notified if there is a change in callstate (for example). One way or the other, at some point, you have found the call you want to answer. Now you need to make sure, that the call is in an alerting state (CS_OFFERING for inbound calls), before you can finally call the answer method.

        try
        {
            ec.Next(1, out ici, ref arg);
            if (ici != null && ici.CallState == CALL_STATE.CS_OFFERING)
            {
                ITBasicCallControl2 bc = (TAPI3Lib.ITBasicCallControl2)ici;
                if (bc != null)
                {
                    bc.Answer();
                }
            }
        }
        catch (Exception exp)
        {
            COMException comEx = exp as COMException;
            if (comEx != null)
                MessageBox.Show(comEx.ErrorCode.ToString());
            else
                MessageBox.Show(exp.Message);
        }

If the call you want to answer is not in the callstate CS_CONNECTED, the method will throw a COMException with an error code of 0x800040010.

For further information on the ITTAPIEventNotification interface, see https://msdn.microsoft.com/en-us/library/windows/desktop/ms732506(v=vs.85).aspx

EDIT:

If you want to detect new incoming calls, I'd recommend to use the TE_CALLNOTIFICATION-Event, because it is triggered only once per new incoming call. The TE_CALLSTATE-Event will be triggered every time the callstate changes.

Now, i've updated the callnotification class:

    public class callnotification : TAPI3Lib.ITTAPIEventNotification
    {
        public InboundCall OnNewIncomingCall;

        public void Event(TAPI_EVENT TapiEvent, object pEvent)
        {
            switch (TapiEvent)
            {
                case TAPI_EVENT.TE_CALLNOTIFICATION:
                    this.OnCallNotification((ITCallNotificationEvent)pEvent);
                    break;
            }
        }

        private void OnCallNotification(ITCallNotificationEvent callNotification)
        {
            ITCallInfo ici = callNotification.Call;

            if (ici != null && ici.CallState == CALL_STATE.CS_OFFERING)
                this.OnNewIncomingCall(ici);
        }
    }

I've also declared a delegate Method to use if there is a new inbound call:

public delegate void InboundCall(ITCallInfo ici);

So your initialization of the callnotification event could look like this:

        callnotification cn = new callnotification();
        cn.OnNewIncomingCall += this.OnNewIncomingCall;

And finally, in the OnNewIncomingCallMethod, you can answer the call:

    private void OnNewIncomingCall(ITCallInfo ici)
    {
        ITBasicCallControl bcc = (ITBasicCallControl)ici;
        if (bcc != null)
        {
            string caller = ici.get_CallInfoString(CALLINFO_STRING.CIS_CALLERIDNUMBER);
            DialogResult dlg = MessageBox.Show(string.Format("New incoming call from {0}\r\nDo you wish to answer the call now?", caller), "New incoming call", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (dlg == System.Windows.Forms.DialogResult.Yes)
                bcc.Answer();
        }
    }

I've tested your code with the additions of mine and it worked fine. Should you be having any exceptions when answering or during the initialization, let me know.