C# - LINQ (Join Table On Multiple Columns, Inside Method Call)

private static int count = 0;

private static int GetUnknownCount(IEnumerable<string> Bibs, 

                                   IEnumerable<string> LotNum, 

                                   IEnumerable<string> SplitLevel, 

                                   IEnumerable<string> ReburnLevel)

 {

     List<LotReport> lotreport2 = lotreport.Where(a => a.Process == "BurnIn").ToList();

     count = 0;

     List<string> mbib = Bibs.ToList();

     List<string> mLotNum = LotNum.ToList();

     List<string> mSplitLevel = SplitLevel.ToList();

     List<string> mReburnLevel = ReburnLevel.ToList();

     for (int i = 0; i < mbib.Count(); i++)

     {

         var bib = mbib[i].ToString();

         var lot = mLotNum[i].ToString();

         var splitlevel = mSplitLevel[i].ToString();

         var reburnlevel = mReburnLevel[i].ToString();

         foreach (var item in lotreport2)

         {

             if (item.LotNum == lot && item.SplitLevel == splitlevel

                  && item.ReburnLevel == reburnlevel && item.BIB == bib)

             {

                 if (item.ResultType == "Unknown")

                 {

                     count += int.Parse(item.Total);

                 }

             }

         }

     }

     return count;

 } 

private void button1_Click(object sender, EventArgs e)

{           

    List<LotReport> lotreport1 = lotreport.Where(a => a.Process == "Bin2").ToList();

    List<LotReport> lotreport2 = lotreport.Where(a => a.Process == "BurnIn").ToList();

    // Join Table On Multiple Columns

    var list3 =  from t1 in lotreport1

                join t2 in lotreport2

                on new { X = t1.LotNum, Y = t1.SplitLevel, Z = t1.ReburnLevel, 

                         W = t1.BIB ,  V = t1.ResultType } equals

                   new { X = t2.LotNum, Y = t2.SplitLevel, Z = t2.ReburnLevel,

                         W = t2.BIB, V = t2.ResultType }

                select new Table

                {

                    LotNum = t1.LotNum,

                    Process = t1.Process,

                    FreshLot = t1.FreshLot,

                    SplitLevel = t1.SplitLevel,

                    ReburnLevel = t1.ReburnLevel,

                    BIB = t1.BIB,

                    FD_Bin2 = t1.FD_Bin2,

                    FD_BurnIn = t2.FD_BurnIn,

                    ResultType = t1.ResultType,

                    Total = t1.Total,

                    ZeroCount = t1.ZeroCount.ToString(),

                    UnknownCount = t1.UnknownCount.ToString()

                };

    // Inside Method Call

    IEnumerable<TableB> list4 = lotreport1.GroupBy(a => new {

                                      a.FreshLot,

                                    })

                                    .Select(b => new TableB {

                                        LotNum = b.Select(c => c.LotNum),

                                        Process = b.Select(c => c.Process),

                                        FreshLot = b.Select(c => c.FreshLot),

                                        SplitLevel = b.Select(c => c.SplitLevel),

                                        ReburnLevel = b.Select(c => c.ReburnLevel),

                                        BIB = b.Select(c => c.BIB),

                                        FD_Bin2 = b.Select(c => c.FD_Bin2),

                                        FD_BurnIn = b.Select(c => c.FD_BurnIn),

                                        ResultType = b.Select(c => c.ResultType),

                                        Total = b.Select(c => c.Total),

                                        ZeroCount = b.Sum(c => c.ResultType == "Pass" ?

                                                               (c.Total == "0" ? 1 : 0 ) : 0 ),

                                        UnknownCount = GetUnknownCount(b.Select(c =>

                                                                  c.ResultType == "Pass" ?

                                                                  (c.Total == "0" ?

                                                                  c.BIB : string.Empty) :

                                                                  string.Empty),

                                                                 b.Select(c =>

                                                                  c.ResultType == "Pass" ?

                                                                  (c.Total == "0" ?

                                                                  c.LotNum : string.Empty) :

                                                                  string.Empty),

                                                                 b.Select(c =>

                                                                  c.ResultType == "Pass" ?  

                                                                  (c.Total == "0" ?

                                                                  c.SplitLevel : string.Empty) :

                                                                  string.Empty),

                                                                 b.Select(c =>

                                                                  c.ResultType == "Pass" ?

                                                                  (c.Total == "0" ?

                                                                  c.ReburnLevel :

                                                                  string.Empty) :

                                                                         string.Empty)),

                                     }).ToList();

           

}