LINQ query with Mutliple Tables?

Question

I am joining the two tables using LINQ to match model class like below



      

  lstOptInInterest = new LinkedList<OptInInterestArea>
                           ((from a in dbEntities.SUBCODE
                           from appCode in dbEntities.CODE.Where(
                              x => x.CODE == a.CODE  && x.TYPE == a.TYPE)
                            select new OptInInterestArea()
                            {
                                   Code = a.CODE,
                                   SubCode = a.SUBCODE,
                                   SubCodeDescription = a.DESCR,
                                   CodeDescription = appCode.DESCR
                              }).ToList());

Model class
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public class OptInInterestArea
    {      
            [DisplayName("Code")]
            public string Code { get; set; }
         
            [DisplayName("Sub Code")]
            public string SubCode { get; set; }
           
    	    DisplayName("Sub Code Description")]
            public string SubCodeDescription { get; set; }
            
    		[DisplayName("Code Description")]
            public string CodeDescription { get; set; }
    
            [DisplayName("Previous OptIn")]
            public bool PrevOptIn { get; set; }
    }

Table B
--



Now my question is I need to assign `PrevOptIn` values of `lstOptInInterest`  from Table B (see above). Table B may or may not contains all of `CODE` and `SUBCODE` of `lstOptInInterest`. 

If `CODE` and `SUBCODE` of `lstOptInInterest` exists on the table B assign to `PrevOptIn` in  else `PrevOptIn = N`

How can I do LINQ to get this? 

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ItsMeSri MOSS SP2, 3 WEFs, Windows 2008 R2 x64.