c#比较集合

本文关键字：集合 比较 | 更新日期: 2023-09-27 18:12:36

我是c#新手，需要一些比较集合的帮助。我有两个List<string>集合，其内容如下:

收集旧:{"AAA"、"BBB"、"CCC"}

收集新:{" BBB ","CCC"、"DDD"}

我想要一个像下面这样的集合:

集合最终:{"AAA","删除";"BBB"、"保持";"CCC"、"保持";"DDD","添加"}

我该怎么做?

c#比较集合

old.Except(new)会给你那些要删除的项目

new.Except(old)会给你添加的项目

old.Intersect(new)会给你物品保存

(这是假设你不介意使用系统。Linq命名空间)

或者，如果您愿意，您可以单独考虑每个项并检查每个列表中的存在

            var oldList = new List<String>() {"AAA", "BBB", "CCC"};
            var newList = new List<String>() {"BBB", "CCC", "DDD"};
            var diffDictionary = new Dictionary<string, string>();
            foreach (var oldEntry in oldList)
            {
                diffDictionary.Add(oldEntry, "Remove");
            }
            foreach (var newEntry in newList)
            {
                if (diffDictionary.ContainsKey(newEntry))
                {
                    diffDictionary[newEntry] = "Keep";
                }
                else
                {
                    diffDictionary.Add(newEntry, "Add");
                }
            }
            foreach (var dDico in diffDictionary)
            {
                Console.WriteLine(string.Concat("Key: ", dDico.Key, " Value: ", dDico.Value));
            }

您可以使用字典来完成此操作…

最后，字典中的每个元素会告诉你每种元素被删除或添加了多少项。

它将用一个计数来表示，而不是简单的3个状态标志…这是因为你可能添加或删除了重复的项目……如果在第二个集合中插入3个AAA呢? 

        string[] col1 = new string[] { "AAA", "BBB", "CCC" };
        string[] col2 = new string[] { "BBB", "CCC", "DDD" };
        Dictionary<string, int> colDic = new Dictionary<string, int>();
        foreach (var item in col1)
        {
            int num;
            if (colDic.TryGetValue(item, out num))
                colDic[item] = num - 1;
            else
                colDic[item] = -1;
        }
        foreach (var item in col2)
        {
            int num;
            if (colDic.TryGetValue(item, out num))
                colDic[item] = num + 1;
            else
                colDic[item] = 1;
        }

最终结果如下所示:

AAA = -1
BBB = 0
CCC = 0
DDD = 1

一行(sort of)!

string[] colOld = {"AAA","BBB","CCC"};
string[] colNew = {"BBB","CCC","DDD"};
dynamic colALL = (from o in colOld.Union(colNew)
                  select new {Value = o, Action = 
                              colOld.Any(s => s == o) ? 
                                  colNew.Any(s => s == o) ? "Keep" : "Remove" 
                              : "Add"
                           }).ToList();

注意:这是一个开发者的融合转换下面的vb.net的工作-我还没有机会测试c#版本:

 Dim colOld() As String = {"AAA", "BBB", "CCC"}
    Dim colNew() As String = {"BBB", "CCC", "DDD"}
    Dim colALL = (From o As String In colOld.Union(colNew) _
                    Select New With {.Value = o, .Action = _
                                     If(colOld.Any(Function(s) s = o), _
                                        If(colNew.Any(Function(s) s = o), "Keep", "Remove"), _
                                        "Add")}).ToList

如果你有这个方法

public static IEnumerable<T> Concat<T>(params IEnumerable<T>[] sequences)
{
    return sequences.SelectMany(x => x);
}

你应该能够写:

static readonly string Remove = "Remove";
static readonly string Keep = "Keep";
static readonly string Add = "Add";
var result = Concat
(
    old.Except(new).Select(x => new { x, Remove }), 
    old.Intersect(new).Select(x => new { x, Keep }), 
    new.Except(old).Select(x => new { x, Add })
);

当然你可以使用内置的Enumerable.Concat方法，但我觉得我的更优雅。

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