加入LINQ中的Where子句

Question

我有兩個要與ID聯接的表，但是只能從表A中選擇行，其中表B中的值為空。

我嘗試了這個：

var dbXMLSoccerTeams = (from dbXMLSoccerTeam in data.EFXMLSoccerTeam
     where dbXMLSoccerTeam.ID == (from dbMatchTeam in data.EFMatchingTeamIDs
         where dbMatchTeam.SmarketsID == null
         select dbMatchTeam.XMLSoccerID)
     select dbXMLSoccerTeam);

但是我收到一個錯誤，說運算符==不能用於將int與iQueryable int進行比較

Answer 1

嘗試：

var dbXMLSoccerTeams = (from dbXMLSoccerTeam in data.EFXMLSoccerTeam
                        from dbMatchTeam in data.EFMatchingTeamIDs
                        where dbMatchTeam.SmarketsID == null
                        && dbXMLSoccerTeam.ID == dbMatchTeam.XMLSoccerID
                        select dbXMLSoccerTeam)

Answer 2

在我看來，您實際上應該使用聯接：

var dbXMLSoccerTeams = from dbXMLSoccerTeam in data.EFXMLSoccerTeam
                       join dbMatchTeam in data.EFMatchingTeamIDs
                         on dbXMLSoccerTeam.ID equals dbMatchTeam.XMLSoccerID
                       where dbMatchTeam.SmarketsID == null
                       select dbXMLSoccerTeam;