简单的LINQ查询

Question

我有一个X项目列表。我想要LINQ查询，将它转换为批量（列表清单），其中每个批次有4个项目，除了最后一个可以有1-4（剩余部分）。此外，数字4应该是可配置的，以便它可以5,17等。

谁能告诉我如何写？

List<Item> myItems = ...; 
List<List<Item>> myBatches = myItems.???? 

预先感谢您！

Answer 1

如果你满意的结果被分类为IEnumerable<IEnumerable<T>>那么你可以这样做：如果你想要一个实际List<List<T>>，那么你就需要添加一些额外的ToList电话

int groupSize = 4; 

var myBatches = myItems.Select((x, i) => new { Val = x, Idx = i }) 
         .GroupBy(x => x.Idx/groupSize, 
           x => x.Val); 

：

int groupSize = 4; 

var myBatches = myItems.Select((x, i) => new { Val = x, Idx = i }) 
         .GroupBy(x => x.Idx/groupSize, 
           x => x.Val, 
           (k, g) => g.ToList()) 
         .ToList(); 

Answer 2

Here是一篇关于使用Take和Skip进行分页的好文章，它与您请求的功能相同。它并没有让你找到一行LINQ，但希望有所帮助。

Answer 3

这让我想到我们在LINQ之前是如何做到这一点的。

var vessels = new List<Vessel>() 
    { new Vessel() { id = 8, name = "Millennium Falcon" }, 
     new Vessel() { id = 4, name = "Ebon Hawk" }, 
     new Vessel() { id = 34, name = "Virago"}, 
     new Vessel() { id = 12, name = "Naboo royal starship"}, 
     new Vessel() { id = 17, name = "Radiant VII"}, 
     new Vessel() { id = 7, name = "Lambda-class shuttle"}, 
     new Vessel() { id = 23, name = "Rogue Shadow"}}; 

var chunksize=2; 

// With LINQ     
var vesselGroups = vessels.Select((v, i) => new { Vessel = v, Index = i }) 
          .GroupBy(c => c.Index/chunksize, c => c.Vessel, (t,e)=>e.ToList()) 
          .ToList(); 

// Before LINQ (most probably not optimal) 
var groupedVessels = new List<List<Vessel>>(); 
var g = new List<Vessel>(); 
var chunk = chunksize; 
foreach(var vessel in vessels) 
{ 
    g.Add(vessel); 
    chunk--; 
    if (chunk == 0) 
    { 
     groupedVessels.Add(g); 
     g = new List<Vessel>(); 
     chunk = chunksize; 
    } 
} 
groupedVessels.Add(g);