是否有任何方法可以将List<SomeObject>分离为SomeObject的几个单独的列表，使用项目索引作为每个分割的分隔符?
让我举个例子:
我有一个List<SomeObject>，我需要一个List<List<SomeObject>>或List<SomeObject>[]，这样每个结果列表将包含一组原始列表的3个项目(依次)。
eg.:
原始列表:[a, g, e, w, p, s, q, f, x, y, i, m, c] 结果列表:[a、g e], [w、p, s], [q, f, x]、[y,我,m], [c]
我还需要结果列表的大小是这个函数的参数。
当前回答
对于任何对打包/维护解决方案感兴趣的人来说，MoreLINQ库提供了符合您所请求行为的批处理扩展方法:
IEnumerable<char> source = "Example string";
IEnumerable<IEnumerable<char>> chunksOfThreeChars = source.Batch(3);
批处理实现类似于Cameron MacFarland的答案，在返回之前添加了用于转换块/批处理的重载，并且性能相当好。
其他回答
另一种方法是使用Rx Buffer操作符
//using System.Linq;
//using System.Reactive.Linq;
//using System.Reactive.Threading.Tasks;
var observableBatches = anAnumerable.ToObservable().Buffer(size);
var batches = aList.ToObservable().Buffer(size).ToList().ToTask().GetAwaiter().GetResult();
我们发现David B的解决方案效果最好。但我们把它改成了一个更普遍的解决方案:
list.GroupBy(item => item.SomeProperty)
.Select(group => new List<T>(group))
.ToArray();
看看这个!我有一个序列计数器和日期的元素列表。每次序列重新启动时，我都想创建一个新列表。
例:消息列表。
List<dynamic> messages = new List<dynamic>
{
new { FcntUp = 101, CommTimestamp = "2019-01-01 00:00:01" },
new { FcntUp = 102, CommTimestamp = "2019-01-01 00:00:02" },
new { FcntUp = 103, CommTimestamp = "2019-01-01 00:00:03" },
//restart of sequence
new { FcntUp = 1, CommTimestamp = "2019-01-01 00:00:04" },
new { FcntUp = 2, CommTimestamp = "2019-01-01 00:00:05" },
new { FcntUp = 3, CommTimestamp = "2019-01-01 00:00:06" },
//restart of sequence
new { FcntUp = 1, CommTimestamp = "2019-01-01 00:00:07" },
new { FcntUp = 2, CommTimestamp = "2019-01-01 00:00:08" },
new { FcntUp = 3, CommTimestamp = "2019-01-01 00:00:09" }
};
我想在计数器重新启动时将列表拆分为单独的列表。代码如下:
var arraylist = new List<List<dynamic>>();
List<dynamic> messages = new List<dynamic>
{
new { FcntUp = 101, CommTimestamp = "2019-01-01 00:00:01" },
new { FcntUp = 102, CommTimestamp = "2019-01-01 00:00:02" },
new { FcntUp = 103, CommTimestamp = "2019-01-01 00:00:03" },
//restart of sequence
new { FcntUp = 1, CommTimestamp = "2019-01-01 00:00:04" },
new { FcntUp = 2, CommTimestamp = "2019-01-01 00:00:05" },
new { FcntUp = 3, CommTimestamp = "2019-01-01 00:00:06" },
//restart of sequence
new { FcntUp = 1, CommTimestamp = "2019-01-01 00:00:07" },
new { FcntUp = 2, CommTimestamp = "2019-01-01 00:00:08" },
new { FcntUp = 3, CommTimestamp = "2019-01-01 00:00:09" }
};
//group by FcntUp and CommTimestamp
var query = messages.GroupBy(x => new { x.FcntUp, x.CommTimestamp });
//declare the current item
dynamic currentItem = null;
//declare the list of ranges
List<dynamic> range = null;
//loop through the sorted list
foreach (var item in query)
{
//check if start of new range
if (currentItem == null || item.Key.FcntUp < currentItem.Key.FcntUp)
{
//create a new list if the FcntUp starts on a new range
range = new List<dynamic>();
//add the list to the parent list
arraylist.Add(range);
}
//add the item to the sublist
range.Add(item);
//set the current item
currentItem = item;
}
下面是我几个月前写的一个列表拆分例程:
public static List<List<T>> Chunk<T>(
List<T> theList,
int chunkSize
)
{
List<List<T>> result = theList
.Select((x, i) => new {
data = x,
indexgroup = i / chunkSize
})
.GroupBy(x => x.indexgroup, x => x.data)
.Select(g => new List<T>(g))
.ToList();
return result;
}
这个怎么样?
var input = new List<string> { "a", "g", "e", "w", "p", "s", "q", "f", "x", "y", "i", "m", "c" };
var k = 3
var res = Enumerable.Range(0, (input.Count - 1) / k + 1)
.Select(i => input.GetRange(i * k, Math.Min(k, input.Count - i * k)))
.ToList();
据我所知，GetRange()与所获取的项目数量是线性的。所以这应该表现得很好。
