c# LINQ用给定的List过滤元组的List

这是pariList(它是List of Tuple)

 List<Tuple<dynamic, dynamic>> PairList = new List<Tuple<dynamic, dynamic>> = 
 {({ Symbol = a, Close = 1.0, Date = 2/1/2016, Vol = 0 }, { Symbol = b, Close = 1.6, Date = 2/1/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.0, Date = 2/1/2016, Vol = 0 }, { Symbol = c, Close = 2.0, Date = 2/1/2016 , Vol = 0 })}  
 {({ Symbol = b, Close = 1.6, Date = 2/1/2016, Vol = 0 }, { Symbol = c, Close = 2.0, Date = 2/1/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.1, Date = 2/2/2016, Vol = 0 }, { Symbol = b, Close = 1.2, Date = 2/2/2016, Vol = 0 })}
 {({ Symbol = a, Close = 1.1, Date = 2/2/2016, Vol = 0 }, { Symbol = c, Close = 2.1, Date = 2/2/2016, Vol = 0 })}   
 {({ Symbol = b, Close = 1.2, Date = 2/2/2016, Vol = 0 }, { Symbol = c, Close = 2.1, Date = 2/2/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.4, Date = 2/3/2016, Vol = 0 }, { Symbol = b, Close = 1.4, Date = 2/3/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.4, Date = 2/3/2016, Vol = 0 }, { Symbol = c, Close = 1.4, Date = 2/3/2016, Vol = 0 })}   
 {({ Symbol = b, Close = 1.4, Date = 2/3/2016, Vol = 0 }, { Symbol = c, Close = 1.4, Date = 2/3/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.7, Date = 2/4/2016, Vol = 0.214285714285714 }, { Symbol = b, Close = 1.8, Date = 2/4/2016, Vol = 0.218217890235992 })}
 {({ Symbol = a, Close = 1.7, Date = 2/4/2016, Vol = 0.214285714285714 }, { Symbol = c, Close = 2.7, Date = 2/4/2016, Vol = 0.464743364189122 })}
 {({ Symbol = b, Close = 1.8, Date = 2/4/2016, Vol = 0.218217890235992 }, { Symbol = c, Close = 2.7, Date = 2/4/2016, Vol = 0.464743364189122 })}
 {({ Symbol = a, Close = 1.8, Date = 2/5/2016, Vol = 0.122450941145067 }, { Symbol = b, Close = 1.2, Date = 2/5/2016, Vol = 0.169725025739105 })}
 {({ Symbol = a, Close = 1.8, Date = 2/5/2016, Vol = 0.122450941145067 }, { Symbol = c, Close = 1.2, Date = 2/5/2016, Vol = 0.301649178342484 })}
 {({ Symbol = b, Close = 1.2, Date = 2/5/2016, Vol = 0.169725025739105 }, { Symbol = c, Close = 1.2, Date = 2/5/2016, Vol = 0.301649178342484 })}
  ......
  ......

现在，我在一个特殊的日期选择一些对

var wantedCombinations = pairList
                        .Where(pair => pair.Item1.Date == Beginday)
                        .Select(pair => new { Item = pair, Volspread = Math.Abs(pair.Item1.Vol - pair.Item2.Vol) })
                        .OrderBy(o => o.Volspread)
                        .Take(FirstSelect)
                        .Select(item =>item.Item)
                        .ToList();

那么如何使'pairList'每个日期只留下wantedCombinations中选择的对。如

选择{a, b}, {a, c}，则pairList变为

 {({ Symbol = a, Close = 1.0, Date = 2/1/2016, Vol = 0 }, { Symbol = b, Close = 1.6, Date = 2/1/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.0, Date = 2/1/2016, Vol = 0 }, { Symbol = c, Close = 2.0, Date = 2/1/2016 , Vol = 0 })}  
 {({ Symbol = a, Close = 1.1, Date = 2/2/2016, Vol = 0 }, { Symbol = b, Close = 1.2, Date = 2/2/2016, Vol = 0 })}
 {({ Symbol = a, Close = 1.1, Date = 2/2/2016, Vol = 0 }, { Symbol = c, Close = 2.1, Date = 2/2/2016, Vol = 0 })}        
 {({ Symbol = a, Close = 1.4, Date = 2/3/2016, Vol = 0 }, { Symbol = b, Close = 1.4, Date = 2/3/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.4, Date = 2/3/2016, Vol = 0 }, { Symbol = c, Close = 1.4, Date = 2/3/2016, Vol = 0 })}   
 {({ Symbol = a, Close = 1.7, Date = 2/4/2016, Vol = 0.214285714285714 }, { Symbol = b, Close = 1.8, Date = 2/4/2016, Vol = 0.218217890235992 })}
 {({ Symbol = a, Close = 1.7, Date = 2/4/2016, Vol = 0.214285714285714 }, { Symbol = c, Close = 2.7, Date = 2/4/2016, Vol = 0.464743364189122 })}
 {({ Symbol = a, Close = 1.8, Date = 2/5/2016, Vol = 0.122450941145067 }, { Symbol = b, Close = 1.2, Date = 2/5/2016, Vol = 0.169725025739105 })}
 {({ Symbol = a, Close = 1.8, Date = 2/5/2016, Vol = 0.122450941145067 }, { Symbol = c, Close = 1.2, Date = 2/5/2016, Vol = 0.301649178342484 })}
  ......
  ......

在一个Linq查询中实现这两个步骤更好吗?

var wantedCombinations = pairList.Where(pair => pair.Item1.Date == Beginday)
                                 .Select(pair => new { Item = pair,  Volspread = Math.Abs(pair.Item1.Vol - pair.Item2.Vol) })
                                 .OrderBy(o => o.Volspread)
                                 .Take(FirstSelect)
                                 .Select(item =>item.Item);
pairList = pairList.Where(pair => 
                        wantedCompinations.Any(wc => wc.Item1.Symbol == pair.Item1.Symbol &&
                                                     wc.Item2.Symbol == pair.Item2.Symbol)).ToList();

var wantedCombinations = new List<dynamic>
{
    new { Symbol1 = "a", Symbol2 = "b" },
    new { Symbol1 = "a", Symbol2 = "c" }
};
var result = pairList.Where(pair => pair.Item1.Date == Beginday &&
                                    wantedCombinations.Any(item => item.Symbol1 == pair.Item1.Symbol &&
                                                      item.Symbol2 == pair.Item2.Symbol))
                     .Select(pair => new { Item = pair, Volspread = Math.Abs(pair.Item1.Vol - pair.Item2.Vol) })
                     .OrderBy(o => o.Volspread)
                     .Take(FirstSelect)
                     .Select(item =>item.Item)
                     .ToList();

var wantedCombinations = new List<dynamic>
{
    new { Symbol1 = "a", Symbol2 = "b" },
    new { Symbol1 = "a", Symbol2 = "c" }
};
var result = (from pair in pairList
             where pait.Item1.Date.Equals(Beginday)
             join c in wantedCombinations on new { pair.Item1.Symbol, pair.Item2.Symbol } equls new { c.Symbol1, c.Symbol2 }
             orderby Math.Abs(pair.Item1.Vol - pair.Item2.Vol)
             select pair).Take(FirstSelect);