Question

我正在尝试根据id列表查找记录。但是当记录被退回时，订单就会丢失我需要按照records中收到的顺序返回list。我该怎么做？

// Select Records from list of id's
public IQueryable<Record> GetRecords(List<int> list)
{
    /*
     * Linq to SQL has a limit on 2100
     */
    var records = Enumerable.Empty<Record>().AsQueryable<Records>();
    var limit = 2000;
    var result = list.Select((value, index) => new { Index = index, Value = value })
             .GroupBy(x => x.Index / limit)
             .Select(g => g.Select(x => x.Value).ToList())
             .ToList();

     foreach (var r in result)
     {
         var row = r;
         records = records.Union(db.Records.Where(a => row.Contains(a.record_id)));
     }
     return records;
}

Answer 1

简单的方法就是这样：

records.Select(x=>new {index = list.IndexOf(x.record_id), record = x})
       .OrderBy(x=>x.index).Select(x=>x.record);

这是O（n ^ 2）但可能有O（n log n）一个。

根据id列表选择记录并保持订单

1 个答案: