Question

可悲的是，我以前做过这件事。我记得搞清楚了。今天，我似乎无法回想起如何做到这一点。

所以你有这个清单：

public List<taters> getTaters(){
    var firstTaters = from s in n.veggies
                      where s.active == true
                     select s.html;

    var secondTaters = from s in n.roots
                      where s.active == true
                     select s.html;

    //now here I want to do something to combine the two 
    //(e.g. a Concat or some such) and   
    //THEN I want to order the concatenated list of results 
    //by 'date_created' descending.  
}

以上评论中的问题。如何将它们加在一起后订购？

Answer 1

firstTaters.Concat(secondTaters)
           .OrderByDescending(html => html.date_created)

还尝试在过滤之前在两个集合上使用串联，以避免代码重复（可能更慢，但更易于维护）

public IEnumerable<taters> getTaters()
{
    return from s in n.veggies.Concat(n.roots)
           where s.active == true
           orderby s.html.date_created descending
           select s.html;
}

不要忘记致电ToList或更改签名以返回IQueryble<taters>或IEnumerable<taters>

Answer 2

使用Concat，或者如果您想要不同的结果，请使用Union

var concated = 
    firstTaters.Concat(secondTaters).OrderByDescending(html => html.date_created);

//Gives distinct values
var unioned = 
    firstTaters.Union(secondTaters).OrderByDescending(html => html.date_created);

Answer 3

或者你可以像下面的例子那样做：

public List<taters> getTaters(){
    var firstTaters = from s in n.veggies
                      where s.active == true
                     select s.html;

    var secondTaters = from s in n.roots
                      where s.active == true
                     select s.html;

    return (
        from first in firstTaters
        join second in secondTaters on secondTaters.someField equals second.someField
        select new 
        {
            ....
            ....
        }
    ).toList();
}

Answer 4

只需添加：

return firstTaters.Concat(secondTaters).OrderByDescending(el => el.DateCreated);

C＃/ LINQ to SQL - 从两个不同的结果集中排序组合结果

4 个答案: