的LINQ - INNER JOIN不是从左表

Question

检索所有记录我曾经做过一个内部联接，它仅显示与以下查询匹配的记录： -

var data = from t1 in ctx.tblEmp 
      join t2 in ctx.tblHelp 
       on t1.Field equals t2.Fld 
      where t1.Id == Id && 
       t2.Id == Id 
      select new Settings { Master = t1.Labelname, OrderNo = t2.OrderNo}; 

我想从tblEmp &唯一匹配的记录中的所有记录从tblHelp。

如何做到这一点？

Answer 1

用作

var data = from t1 in ctx.tblEmp 
     join t2 in ctx.tblHelp 
      on t1.Field equals t2.Fld into u 
      from t2 in u.DefaultIfEmpty() 
     where t1.Id == Id && 
      t2.Id == Id 

     select new Settings { Master = t1.Labelname, OrderNo = t2.OrderNo}; 

试试这个

var data = from t1 in ctx.tblEmp 
     join t2 in ctx.tblHelp 
      on t1.Field equals t2.Fld into u 
      from t2 in u.DefaultIfEmpty() 
     where t1.Id == Id 
     orderby columnname // Added Order By 
     select new Settings { Master = t1.Labelname, OrderNo = t2.OrderNo==null ?"":t2.OrderNo}; 

Answer 2

var query = from t1 in ctx.tblEmp 
        join t2 in ctx.tblHelp on t1 equals t2.Fld into tempGroup 
        from subpet in tempGroup.DefaultIfEmpty() 
        select new { t1.Labelname, OrderNo = (subpet == null ? String.Empty : subpet.OrderNo) };