查询以从多个表中获取信息

Question

我的数据库中有以下标签

1. TestPack {id，name，type}
2. InternalWalk {id，tp_id，date}
3. ExternalWalk {id，tp_id，date}
4. 刷新{id，tp_id，date}
5. PunchItems {id，tp_id，name，type，category，reporteddate，closedDate}

tp_Id是TestPack id，是所有其他表中的外键，这意味着TestPack可能具有1-N内部/外部步行，Flushings和PunchItems。

现在我想查询数据库（使用EF LINQ）以返回测试包，以及针对一个测试包的所有Walks，Flushings，Punchitems，以便我可以在单个DataGrid中显示所有这些信息？

测试包，没有任何Flushings，Walks，PunchItems不应出现在结果中。如果存在任何一个，则应在结果中显示测试包

编辑：

 var queryResult = 
                            from tp in allTestPacks
                            join iwalk in allInternalWalks on tp.id equals iwalk.test_pack_id.Value 
                            into tpIwalk from iwalk in tpIwalk.DefaultIfEmpty()

                            join ewalk in allExternalWalks on tp.id equals ewalk.test_pack_id.Value
                            into tpEwalk from ewalk in tpEwalk.DefaultIfEmpty()

                            join flings in allFlushings on tp.id equals flings.test_pack_id.Value
                            into tpFlings from flings in tpFlings.DefaultIfEmpty()

                            join pitems in allPunchItems on tp.id equals pitems.test_pack_id.Value
                            into tpPitems from pitems in tpPitems.DefaultIfEmpty()
                            select new
                            {
                                TestPackID = tp.test_pack_no,
                                InternalWalkdDate = iwalk != null ? iwalk.RFIDate : null,
                                ExternalWalkDate = ewalk != null ? ewalk.RFIDate : null,
                                FlushinDate = flings != null ? flings.rfi_no : null,
                                PunchItemCategory = pitems != null ? pitems.description : null//etc
                            };

Answer 1

编辑：整理不必要的通行证

var resultset = from tp in allTestPacks
 join iwalk in allInternalWalks on tp.id equals iwalk.test_pack_id.Value into tpIwalk 
 join ewalk in allExternalWalks on tp.id equals ewalk.test_pack_id.Value  into tpEwalk 
 join flings in allFlushings on tp.id equals flings.test_pack_id.Value into tpFlings
 join pitems in allPunchItems on tp.id equals pitems.test_pack_id.Value into tpPitems 

 from iwalk in tpIwalk.DefaultIfEmpty()
 from ewalk in tpEwalk.DefaultIfEmpty()
 from flings in tpFlings.DefaultIfEmpty()
 from pitems in tpPitems.DefaultIfEmpty()

select new
{
 TestPackID = tp.test_pack_no,
 InternalWalkdDate = iwalk != null ? iwalk.RFIDate : null,
 ExternalWalkDate = ewalk != null ? ewalk.RFIDate : null,
 FlushinDate = flings != null ? flings.rfi_no : null,
 PunchItemCategory = pitems != null ? pitems.description : null//etc
};

Console.WriteLine ((System.Data.Objects.ObjectQuery) resultset).ToTraceString();