how to add current timestamp while generating Id

private void ProcessRequestForCommissionProvisioning(Model.ClassObject.Request commissionreq)

{

//code goes here

accReq.ConsumerID = commissionreq.ConsumerID;

accReq.transactionID = "EPDCM_" + commissionreq.ID;

accReq.OperationType = commissionreq.OperationType;

}

Note: Here in this line "accReq.transactionID = "EPDCM_" + commissionreq.ID;"  we are generating new ID 

         How to make sure I add Current timestamp along with this line "accReq.transactionID = "EPDCM_" + commissionreq.ID;"

Please assist me