如何在 linq 查询中设置内连接

Posted 2023-04-12

【中文标题】如何在 linq 查询中设置内连接

【英文标题】：How to set inner join in linq query

【发布时间】：2021-08-03 09:56:29

【问题描述】：

我想在 linq 查询中设置内连接

这是我的代码，

var JoinUsingMS = from emp in _productRepository.Table
   join address in _purchaseReminderRepository.Table
  on new  c1 = emp.VendorId, c2 = emp.Name  equals new  c1 = address.VendorId, c2 = address.Product  into bp_sm
   from c in bp_sm.DefaultIfEmpty()
   where emp.Published == true
   select emp;

从这个查询中，我得到了左连接（通过调试跟踪）。虽然我认为这个查询非常适合内连接（参考链接As Per This Solution）仍然输出得到左连接

【参考方案1】：

下面更新了内部连接的查询：

var JoinUsingMS = from emp in _productRepository.Table
   join address in _purchaseReminderRepository.Table
   on new  c1 = emp.VendorId, c2 = emp.Name  
   equals new  c1 = address.VendorId, c2 = address.Product 
   where emp.Published == true
   select emp;

【参考方案2】：

简单。删除DefaultIfEmpty 行。这就是创建左连接子句的原因：

var JoinUsingMS = 
    from emp in _productRepository.Table
    join address in _purchaseReminderRepository.Table
      on new  c1 = emp.VendorId, c2 = emp.Name  equals new  c1 = address.VendorId, c2 = address.Product  // into bp_sm
    // from c in bp_sm.DefaultIfEmpty()
    where emp.Published == true
    select emp;