带有LINQ中的联接的Union的匿名类型错误

Question

我正在尝试在多个表上执行联合以产生总加仑数的燃料。有些表只有一列加仑燃料，而其他表有两列或三列。我在Visual Studio 2013 LINQing中使用.NET 4.5和Entity Framework 6进行SQL Server 2012中的数据。

Visual Studio 2013向我提供了'Anonymous Type # 1' does not contain a definition for 'Union' and no extension method 'Union' accepting a first argument of type 'Anonymous Type # 1' could be found (are you missing a using directive or an assembly reference?)我在其他有关匿名类型的文章中看到的错误，并且仍然不清楚修改代码的最佳方法。 Visual Studio指出的错误位于包含关键字Union的var fueltable行中，靠近底部。所有“加仑”列的数据类型都是十进制数，因此我不确定要更改的数据类型。我应该将Union放在其他地方，还是改变类型，或完全不同的东西？任何建议都表示赞赏。

  public IHttpActionResult FuelTax(FuelTaxBindingModel fuelinfo)

  {

    ...

    var trucks = Array.ConvertAll<Trucks ,string>
                (fuelinfo.selectedTrucks,
                 x=>x.FT_Tractor.ToString() ).ToArray();

    var temptable1 = (from t1 in db.FuelTaxDetails 
                           join t2 in db.FuelTaxes 
                             on t1.FTD_FT_Key equals t2.FT_Key
                           join t3 in db.OtherFuelTransactions
                             on t2.FT_API_Apl_Key equals t3.api_key
                      where (t2.FT_API_Apl_Key == fuelinfo.apikey)
                             && (t2.FT_LoadDate >= fuelinfo.beginningDate 
                             && t2.FT_LoadDate <= fuelinfo.endDate)
                             && (trucks.Contains(t2.FT_Tractor))
                      select new { t1.FTD_State, t1.FTD_Miles, t1.FTD_NonToll,
                                        t1.FTD_Toll, t3.Gallons };

    var temptable2 = (from a in db.FuelTaxDetails
                          join b in db.FuelTaxes
                            on a.FTD_FT_Key equals b.FT_Key
                          join t4 in db.ComdataTranslations
                            on b.FT_API_Apl_Key equals t4.API_Key
                          join t5 in db.ComdataTransactions
                            on t4.Comdata_Key equals t5.CDNCompanyCode
                      let Gallons = t5.NumberofTractorGallons 
                                     + t5.NumberofReeferGallons
                                     + t5.OtherFuelGallons
                      where (b.FT_API_Apl_Key == fuelinfo.apikey)
                             && (b.FT_LoadDate >= fuelinfo.beginningDate 
                             && b.FT_LoadDate <= fuelinfo.endDate)
                             && (trucks.Contains(b.FT_Tractor))
                      select new { a.FTD_State, a.FTD_Miles, 
                                   a.FTD_NonToll, a.FTD_Toll,
                                   Gallons });

    ... 

    var fueltable = temptable1.Union(temptable2)
                    .OrderBy(s => s.FTD_State)
                    .GroupBy(s => new { s.FTD_State })
                    .Select(g => new
                    {
                     FTD_State = g.Key.FTD_State,
                     FTD_Miles = g.Sum(x => x.FTD_Miles),
                     FTD_NonToll = g.Sum(x => x.FTD_NonToll),
                     FTD_Toll = g.Sum(x => x.FTD_Toll),
                     Gallons = g.Sum(x => x.Gallons)
                    });