Question

我无法获得在Mono中工作的请求：没有连接就可以了。当我只选择t1时它也有效，但我无法从两个表中选择一些东西。我想我想要一个左连接，我总是在t1中有条目，如果NameOfFile与FileName匹配，那么我想要连接表。

额外问题：我的查询何时执行？当我运行foreach循环时？

var result = (
            from t1 in db.Table1 
            join t2 in db.Table2 on t1.FileName equals t2.NameOfFile
            into joinDep                
            from t3 in joinDep.DefaultIfEmpty () 
            select new 
            {
            Time = t1.WriteTime,
            Name = t2.NameOfFile

            }
        )
        .OrderByDescending (c => c.Time.Date)
        .Take (10);
foreach (var entry in result)
{
    Console.WriteLine (entry.Name );
}

Answer 1

使用此：

var query = from t1 in db.Table1 
            join t2 in db.Table2 on t1.FileName equals t2.NameOfFile into gj
            from joinDep in gj.DefaultIfEmpty ()
            select new 
            {
               Time = t1.WriteTime,
               Name = joinDep.NameOfFile
            };

var result = query.OrderByDescending (c => c.Time.Date)
                .Take (10);

是。 Take使用延迟执行。

Linq 2 SQL左边加入单声道

1 个答案: