右联结换汤不换药，这个联结的概念不仅适用于SQL，对象列表也可以
var list = (from objSubject in listSubjectDetail join objBalance in listBalance on objSubject.AccountSubjectDetail equals objBalance.GameChannelName into temp from tt in temp.DefaultIfEmpty() select new { objSubject.AccountSubject, objSubject.AccountSubjectDetail, InitialBalance = tt == null ? 0 : tt.Balance, objSubject.DebitAmount, objSubject.CreditAmount, //join为空时的处理 FinalBalance = (tt == null ? 0 : tt.Balance) + objSubject.DebitAmount - objSubject.CreditAmount, objSubject.JournalEntryTime }).ToList();多表连接
var query = from t1 in dt.AsEnumerable() join t2 in dt2.AsEnumerable() on t1.Field<int>("Addressid") equals t2.Field<int>("Addressid") into tmp join t3 in dt3.AsEnumerable() on t1.Field<int>("userid") equals t3.Field<int>("userid") from t in tmp.DefaultIfEmpty() orderby t1.Field
(
"insertdate")
descending
select
new { Name = t1.Field<
string>(
"Name"), RealName = (t ==
null) ?
string.Empty : t.Field<
string>(
"RealName"), nickname = t3.Field<
string>(
"nickname") };
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