Hi @vaibhav.korade
You can request an instrument by passing an OMMItemIntSpec that contain request message to the RegisterClient() call.

reqMsg.MsgModelType = ThomsonReuters.RFA.RDM.RDM.MESSAGE_MODEL_TYPES.MMT_MARKET_PRICE; 
reqMsg.InteractionType = ReqMsg.InteractionTypeFlag.InitialImage | ReqMsg.InteractionTypeFlag.InterestAfterRefresh;
attribInfo.NameType = ThomsonReuters.RFA.RDM.RDM.INSTRUMENT_NAME_TYPES.INSTRUMENT_NAME_RIC;
attribInfo.Name = new RFA_String("TRI.N");
attribInfo.ServiceName = new RFA_String("IDN_RDF");
reqMsg.AttribInfo = attribInfo;
ommItemIntSpec.Msg = reqMsg;
long itemHandle = ommConsumer.RegisterClient(eventQueue, ommItemIntSpec, this);

But if you want to request multiple instruments within a single request. You have to use batch request.

reqMsg.MsgModelType = ThomsonReuters.RFA.RDM.RDM.MESSAGE_MODEL_TYPES.MMT_MARKET_PRICE;
reqMsg.InteractionType = ReqMsg.InteractionTypeFlag.InitialImage | ReqMsg.InteractionTypeFlag.InterestAfterRefresh;
attribInfo.NameType = ThomsonReuters.RFA.RDM.RDM.INSTRUMENT_NAME_TYPES.INSTRUMENT_NAME_RIC;
attribInfo.ServiceName = new RFA_String("IDN_RDF");
reqMsg.AttribInfo = attribInfo;
//Set Batch Request Flag
reqMsg.IndicationMask = ReqMsg.IndicationMaskFlag.Batch;
//Set itemList in payload.
ElementList elementList = new ElementList();
ElementEntry element = new ElementEntry();
ElementListWriteIterator elwiter = new ElementListWriteIterator();
elwiter.Start(elementList);
ArrayWriteIterator arrWIt = new ArrayWriteIterator();
ThomsonReuters.RFA.Data.Array elementData = new ThomsonReuters.RFA.Data.Array();
//Encode a ItemList for batch
arrWIt.Start(elementData);
DataBuffer dataBuffer = new DataBuffer();
ArrayEntry arrayEntry = new ArrayEntry();
{
dataBuffer.Clear();
arrayEntry.Clear();
dataBuffer.SetFromString(new RFA_String("JPY="), DataBuffer.DataBufferEnum.StringAscii);
arrayEntry.Data = dataBuffer;
arrWIt.Bind(arrayEntry);
}
{
dataBuffer.Clear();
arrayEntry.Clear();
dataBuffer.SetFromString(new RFA_String("EUR="), DataBuffer.DataBufferEnum.StringAscii);
arrayEntry.Data = dataBuffer;
arrWIt.Bind(arrayEntry);
}
arrWIt.Complete();
element.Name = RDM.RDM.REQUEST_MSG_PAYLOAD_ELEMENT_NAME.ENAME_BATCH_ITEM_LIST;
element.Data = elementData; elwiter.Bind(element);
elwiter.Complete();
reqMsg.Payload = elementList;
ommItemIntSpec.Msg = reqMsg;
long itemHandleBatch = ommConsumer.RegisterClient(eventQueue, ommItemIntSpec, this);

There is an example called “StarterConsumer_BatchView”. This example shows how to use batch request.

Once you request instruments, API will send request message to server and server will response with either refresh message, if the request is success, or status message, if the request is fail (for example: no permission).
The response message will enter the ProcessEvent() callback which you can extract the message from the event. See QuickStartConsumer’s ProcessEvent() for example.