将SQL查询转换为Linq（包含左联接）

我认为您的SQL的直接翻译看起来像这样：

var q = from ds in table1        where ds.SubmissionTypeId == 1 || ds.SubmissionTypeId == 2        from di in table2        from dr in table2        where (ds.SubmissionTypeId == 2 && ds.SubmissionId == di.Id)|| (ds.SubmissionTypeId == 1 && ds.SubmissionId == dr.Id)        select ds;

但是，这似乎不太可能是您想要的。如果我推测您的预期逻辑是什么，我认为您想要更多类似这样的东西：

var q = from ds in table1        where (ds.SubmissionTypeId == 2 && table2.Any(di => ds.SubmissionId == di.Id))|| (ds.SubmissionTypeId == 1 && table3.Any(dr => ds.SubmissionId == dr.Id))        select ds;