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

试试下面的代码。

public static List<List<T>> Split<T>(IList<T> source)
{
    return  source
        .Select((x, i) => new { Index = i, Value = x })
        .GroupBy(x => x.Index / 3)
        .Select(x => x.Select(v => v.Value).ToList())
        .ToList();
}

其思想是首先根据索引对元素进行分组。除以3的效果是把它们分成3组。然后将每个组转换为一个列表,将list的IEnumerable转换为list的list

其他回答

public static List<List<T>> GetSplitItemsList<T>(List<T> originalItemsList, short number)
    {
        var listGroup = new List<List<T>>();
        int j = number;
        for (int i = 0; i < originalItemsList.Count; i += number)
        {
            var cList = originalItemsList.Take(j).Skip(i).ToList();
            j += number;
            listGroup.Add(cList);
        }
        return listGroup;
    }

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;
}

如果列表的类型为system.collections.generic,则可以使用“CopyTo”方法将数组中的元素复制到其他子数组中。您可以指定开始元素和要复制的元素数量。

你也可以对你的原始列表做3个克隆,并在每个列表上使用“RemoveRange”将列表缩小到你想要的大小。

或者只是创建一个helper方法来为您做这件事。

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;
        }

从。net 6开始,你现在可以使用原生Chunk()方法,可用于IEnumerable<T>和IQueryable<T>。

更多信息(和链接)在这里:https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/partitioning-data