C#学习教程：由于，无法与Linq一起使用.Union分享

我有点困惑于这个问题。 希望我会得到一些帮助。 这就是重点。 我必须用我的SQL请求填充我的DataGridView：

SELECT LOT.NumLot, EtatLot, NomEmploye FROM LOT JOIN AFFECTATION_LOT on LOT.NumLot=AFFECTATION_LOT.NumLot JOIN EMPLOYE on AFFECTATION_LOT.IdEmploye=EMPLOYE.IdEmploye WHERE EtatLot='Libéré' or EtatLot='Suspendu' or EtatLot='Démarré' UNION SELECT NumLot, EtatLot, null FROM LOT WHERE EtatLot='Démarré' 

首先，我在第二个“SELECT”中使用了“null”值，因为“UNION”需要有3个参数，如第一个“SELECT”，并且我的表LOT中没有“NomEmploye”数据。 无论如何，该请求在SQL中运行良好。 但是当我尝试在LINQ中使用它时

 string test = "null"; var listeLotCOntrole= (from x in entBoum.LOT join aff in entBoum.AFFECTATION_LOT on x.NumLot equals aff.NumLot join emp in entBoum.EMPLOYE on aff.IdEmploye equals emp.IdEmploye where x.EtatLot.Contains("Libéré") || x.EtatLot.Contains("Suspendu") || x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, emp.NomEmploye }).Union (from x in entBoum.LOT where x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, test }); dataGridViewAffectationLotControleur.DataSource = listeLotControle.ToList(); 

我在Visual Studio中有3个错误，我真的不明白它。

 Error 1 Argument instance: can not convert 'System.Linq.IQueryable AnonymousType # 1>' to 'System.Linq.ParallelQuery ' Error 2 'System.Linq.IQueryable ' does not contain a definition for 'Union' and the best overload the extension method 'System.Linq.ParallelEnumerable.Union  (System.Linq.ParallelQuery , System.Collections.Generic.IEnumerable ) ' Error 3 type arguments for method 'System.Linq.Enumerable.ToList  (System.Collections.Generic.IEnumerable )' can not be inferred from the use. Try specifying the type arguments explicitly. 

正如我所看到的，问题是由于 &＃8230;.但是这对我现在没那么帮助。 我也试过这种方式让它发挥作用

 IQueryable listeLotControle; string test = "null"; listeLotCOntrole= (from x in entBoum.LOT join aff in entBoum.AFFECTATION_LOT on x.NumLot equals aff.NumLot join emp in entBoum.EMPLOYE on aff.IdEmploye equals emp.IdEmploye where x.EtatLot.Contains("Libéré") || x.EtatLot.Contains("Suspendu") || x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, emp.NomEmploye }).Union (from x in entBoum.LOT where x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, test }); dataGridViewAffectationLotControleur.DataSource = listeLotControle.ToList(); 

但我有同样的错误加上那一个

 Error 4 'System.Linq.IQueryable' does not contain a definition for 'ToList' and no extension method 'ToList' accepting a first argument of type 'System.Linq.IQueryable' was found (a using directive or an assembly reference is it missing?) 

我可能需要一个使用，但哪一个？ （我确切地说，我已经使用using System.Linq; ）

最后我尝试了最后一种方法。

 string test = "null"; var listeLotCOntrole= from x in entBoum.LOT join aff in entBoum.AFFECTATION_LOT on x.NumLot equals aff.NumLot join emp in entBoum.EMPLOYE on aff.IdEmploye equals emp.IdEmploye where x.EtatLot.Contains("Libéré") || x.EtatLot.Contains("Suspendu") || x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, emp.NomEmploye }; var listeLotControle2 = from x in entBoum.LOT where x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, test }; var union = listeLotControle.Union(listeLotControle2); dataGridViewAffectationLotControleur.DataSource = listeLotControle2.ToList(); 

但我仍然有这些错误

 Error 1 'System.Linq.IQueryable ' does not contain a definition for 'Union' and the best overload the extension method 'System.Linq.ParallelEnumerable.Union  (System.Linq.ParallelQuery , System.Collections.Generic.IEnumerable ) 'contains invalid arguments Error 2 Argument instance: can not convert 'System.Linq.IQueryable ' to 'System.Linq.ParallelQuery ' 

对不起那块大块但是我试着在问你之前解释我所做的一切。 感谢您将来的答案。

 var listeLotCOntrole= ( from x in entBoum.LOT join aff in entBoum.AFFECTATION_LOT on x.NumLot equals aff.NumLot join emp in entBoum.EMPLOYE on aff.IdEmploye equals emp.IdEmploye where x.EtatLot.Contains("Libéré") || x.EtatLot.Contains("Suspendu") || x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, emp.NomEmploye } ).Union ( from x in entBoum.LOT where x.EtatLot.Contains("Démarré") select new { x.NumLot, x.EtatLot, NomEmploye = test } ); 

 select new { x.NumLot, x.EtatLot, emp.NomEmploye }; 

 select new { x.NumLot, x.EtatLot, test };