Modify LINQ query to accommodate search criteria

Question

 I have the following LINQ statement


  var transaction = (from sst in Context.Transactions
                         join sstcnt in (
                             from ssti in _recorderContext.TransactionItems
                             group ssti by ssti.TransactionId into g
                             select new { TransactionId = g.Key, NumItemId = g.Count() }
                         ) on sst.TransactionId equals sstcnt.TransactionId
                         join ssti in Context.TransactionItems on sst.TransactionId equals ssti.TransactionId
                         where ssti.TransactionId == trans.TransactionId 
                               orderby sst.Created descending
                         select  new object[]
                         {
                                sst.TransactionId,
                                sst.Status,
                               
                         }
                         ).ToList();

 I have these 5 text boxes in my GUI:


	 FullName  Trans#    EmailAddress Phonenumber


 If the employee only enters partial FullName and other text are either empty or full then I want to modify my LINQ query
to do the search on the data entered by the employee so for e.g. If the employee enters

		                 peter for fullName
						 Trans# is empty
						 emialAddress is partial
						 Phone number is empty 


	 then I want to do the search based on whatever data has been entered in the textboxes by the employee
						 if all the text boxes are empty except one of them is full then I want to do the search based on only the data that is entered in that text boxes. How can Modify my LINQ query to 
						 do this kind of search