Working with TAPI 3.0 in our application (With Basic Call Control Functions)

The first thing you need to do is create the TAPI objects to initialize the TAPI 3.0 TSP (TAPI Service Providers). To have more information on TSP and what TAPI is all about, please refer to help provided in the MSDN .NET documentation. The code below is a declaration of the TAPI object and addresses the interfaces that will hold the addresses which are responsible for call handling, and basic call control interface which will hold the reference to the object that will be responsible for handling basic operations of the call.

private TAPIClass tobj;
private ITAddress[] ia=new TAPI3Lib.ITAddress[10];
private ITBasicCallControl bcc;

The code below is responsible for initializing a TAPI object so that it can be used by application. The main functions are:

* Initialize() will initialize TAPI.
* EnumerateAddresses() will give the list of available TSPs.

void initializetapi3()
{
try
{
tobj = new TAPIClass();
tobj.Initialize();
IEnumAddress ea=tobj.EnumerateAddresses();
ITAddress ln;
uint arg3=0;
lines=0;

cn=new callnotification();
cn.addtolist=new callnotification.listshow(this.status);
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);

for(int i=0;i<10;i++)
{
ea.Next(1,out ln,ref arg3);
ia[i]=ln;
if(ln!=null)
{
comboBox1.Items.Add(ia[i].AddressName);
lines++;
}
else
break;
}
}
catch(Exception e)
{
MessageBox.Show(e.ToString());
}
}

The code below is responsible for registering incoming calls so that they can be handled by our application. For that you need to select the line on which you want to receive calls and press the Register button.

try
{
registertoken[line]=tobj.RegisterCallNotifications(ia[line],
true,true,TapiConstants.TAPIMEDIATYPE_AUDIO,2);
MessageBox.Show("Registration token : "+
registertoken[line],
"Registration Succeed for line "+line);
}
catch(Exception ein)
{
MessageBox.Show("Failed to register on line "+line,"Registration for calls");
}

The class given below is to be added depending upon your TAPI event handling requirements. This is specially designed according to the requirements of the application.

class callnotification:TAPI3Lib.ITTAPIEventNotification
{
public delegate void listshow(string str);
public listshow addtolist;

public void Event(TAPI3Lib.TAPI_EVENT te,object eobj)
{
switch(te)
{
case TAPI3Lib.TAPI_EVENT.TE_CALLNOTIFICATION:
MessageBox.Show("call notification event has occured");
break;
case TAPI3Lib.TAPI_EVENT.TE_DIGITEVENT:
TAPI3Lib.ITDigitDetectionEvent dd =
(TAPI3Lib.ITDigitDetectionEvent)eobj;
MessageBox.Show("Dialed digit"+dd.ToString());
break;
case TAPI3Lib.TAPI_EVENT.TE_GENERATEEVENT:
TAPI3Lib.ITDigitGenerationEvent dg =
(TAPI3Lib.ITDigitGenerationEvent)eobj;
MessageBox.Show("digit dialed!");
MessageBox.Show("Dialed digit"+dg.ToString());
break;
case TAPI3Lib.TAPI_EVENT.TE_PHONEEVENT:
MessageBox.Show("A phone event!");
break;
case TAPI3Lib.TAPI_EVENT.TE_GATHERDIGITS:
MessageBox.Show("Gather digit event!");
break;
case TAPI3Lib.TAPI_EVENT.TE_CALLSTATE:
TAPI3Lib.ITCallStateEvent a=
(TAPI3Lib.ITCallStateEvent)eobj;
TAPI3Lib.ITCallInfo b=a.Call;
switch(b.CallState)
{
case TAPI3Lib.CALL_STATE.CS_INPROGRESS:
MessageBox.Show("dialing");
break;
case TAPI3Lib.CALL_STATE.CS_CONNECTED:
MessageBox.Show("Connected");
break;
case TAPI3Lib.CALL_STATE.CS_DISCONNECTED:
MessageBox.Show("Disconnected");
break;
case TAPI3Lib.CALL_STATE.CS_OFFERING:
MessageBox.Show("A party wants to communicate with you!");
break;
case TAPI3Lib.CALL_STATE.CS_IDLE:
MessageBox.Show("Call is created!");
break;
}
break;
}
}
}

How to handle H.323 or IP calls????

To do IP calls or H.323 calls, you need to make H.323 call(IP call) enabled and enter the IP address of the destination and Call. Otherwise it will not succeed in calling to the remote destination. To receive H.323 calls or IP calls, you need to first register on the line on which you want to receive IP calls and h.323 call(IP call).
How to answer an incoming call

BasicCallCOntrol.Answer(), is enough to answer a call.

How to transfer a call:

To transfer a call, first there should be one active call existing. Then you can specify the address to which the call is to be transferred to
Here I have specified the internet address since the call was an IP call. To provide this functionality, there is one function in IBasicCallControl named BlindTransfer(String transfferaddress). Refer the MSDN documents for more information on that!