linq to sql是否具有with ties选项? [英] Does linq to sql have a with ties option?

问题描述

我正在尝试将以下查询移至Linq-to-sql，这可能吗?

I'm trying to move the following query to Linq-to-sql, is it possible?

select * from (
Select top (@Percent) percent with ties *
from(
    Select distinct
      LoanNumber as LoanNo
    From CHE 
    Left Join RecordingInfo as Rec
    On CHE.LoanNumber = Rec.LoanNo
    Where Channel = 'LINX'
        and CHE.Doc in ('MTG','MOD')
        and Rec.LoanNo is null
        and LoanNumber >= '@LoanNo'
) A
order by LoanNo @Order
) B
order by LoanNo

我还没有发现与linq中的关系有关.

I have not seen anyway to do with ties in linq.

推荐答案

我认为类似的方法对您有用.

I think something like this will work for you.

public static IQueryable<T> TopPercentWithTies<T, TKey>(this IOrderedQueryable<T> query, Expression<Func<T, TKey>> groupByExpression, double percent)
{
    var groupedQuery = query.GroupBy(groupByExpression);
    int numberToTake = groupedQuery.Count() * percent / 100;
    return groupedQuery.Take(numberToTake).SelectMany(t => t);
}

我仅使用IEnumerable对其进行了测试，因此我不确定它是否可以与IQueryable一起正常使用.在调用TopPercentWithTies()之前，我还对列表进行了排序.

I only tested it with IEnumerable, so I don't know for sure that it'll work properly with IQueryable. I also sorted the list before calling TopPercentWithTies().

这是我用来测试的代码.

Here's the code I used to test it.

int percent = 50;
var people = new []
{
    new { Age = 99, Name = "Adam" },
    new { Age = 99, Name = "Andrew" },
    new { Age = 89, Name = "Bob" },
    new { Age = 50, Name = "Cecil" },
    new { Age = 50, Name = "Doug" },
    new { Age = 50, Name = "Everett" },
    new { Age = 35, Name = "Frank" },
    new { Age = 25, Name = "Greg" },
    new { Age = 15, Name = "Hank" }
};
var sortedPeople = people.AsQueryable().OrderByDescending(person => person.Age);
var results = sortedPeople.TopPercentWithTies(person => person.Age, percent);
foreach (var person in results)
    Console.WriteLine(person);

希望它可以帮助或至少使您朝正确的方向发展.您可能需要调整用于计算numberToTake的逻辑.

Hope it helps or at least gets you in the right direction. You may want to tweak the logic for calculating numberToTake.

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