Linq扩展之MoreLinq

MoreLinq在Linq的基础上进行了扩展，大致看了下，摘一些记录，以备后需！

一、ForEachExtension

System.Linq只提供了List的ForEach方法，这里扩展了IEnumerable的ForEach方法

IEnumerable<string> lst = students.Select(p => p.Name);
lst.ForEach(x => Console.WriteLine(x));

二、Join扩展 LeftJoinExtension RightJoinExtension FullJoinExtension

var queryLeftJoin = students.LeftJoin(students2,
                        a => a.Name,
                        b => b.Name,
                        a => new { LeftName = a.Name, RightName = "没找到用户" },
                        (a, b) => new { LeftName = a.Name, RightName = b.Name });
queryLeftJoin.ForEach(x => {
    Console.WriteLine($"{x.LeftName}-{x.RightName}");
});
            
var queryRightJoin = students.RightJoin(students2,
                        a => a.Name,
                        b => b.Name,
                        b => new { LeftName = "没找到用户", RightName = b.Name },
                        (a, b) => new { LeftName = a.Name, RightName = b.Name });
queryRightJoin.ForEach(x => {
    Console.WriteLine($"{x.LeftName}-{x.RightName}");
});
            
var queryFullJoin = students.FullJoin(students2,
                        a => a.Name,
                        b => b.Name,
                        a => new { LeftName = a.Name, RightName = "没找到用户" },
                        b => new { LeftName = "没找到用户", RightName = b.Name },
                        (a, b) => new { LeftName = a.Name, RightName = b.Name });
queryFullJoin.ForEach(x => {
    Console.WriteLine($"{x.LeftName}-{x.RightName}");
});

三、InsertExtension 从前插入列表; BacksertExtension 从后插入列表

对于无序加入新的列表，还是挺方便的

var InsertTest = new string[] { "a", "b", "c" }.Insert(new string[] { "d" }, 1); //a,d,b,c
var BackInsertTest = new string[] { "a", "b", "c" }.Backsert(new string[] { "d" }, 1); //a,b,d,c

四、ToDataTableExtension 转为数据表

var dt = students.ToDataTable();

五、ShuffleExtension 打乱数据

以一抽奖为例：

//Demo:抽奖 一等奖1个，二等级奖3个
var players = new List<string>() { "刘备", "关羽", "张飞", "赵云", "马超", "黄忠", "魏延", "关平", "关兴", "小兵甲", "小兵乙", "小兵丙", "小兵丁" };
var bonus1 = players.Shuffle().First();
Console.WriteLine("一等奖："   bonus1);

players.Remove(bonus1); //去掉已抽一等奖的人 
           
var bonus2 = players.Shuffle().Take(3).ToList(); //一定要ToList，不然每调用一次都是重新洗牌
Console.WriteLine("二等奖："   String.Join(",", bonus2.ToArray()));

bonus2.ForEach(x => players.Remove(x)); //去掉已抽二等奖的人   

var bonus3 = players.Shuffle().Take(5).ToList();
Console.WriteLine("三等奖："   String.Join(",", bonus3.ToArray()));

六、CountByExtension 分组统计

//按指定的元素，统计对的数据，类似group分组
var countByResult = new string[] { "a","a", "aa" }.CountBy(p => p);
countByResult.ForEach(x=>Console.WriteLine(x.Key "-" x.Value)); //a-2,aa-1

七、PermutationsExtension 排列; SubsetsExtension 组合;

//排列 Permutations
var set = new[] { "a","b","c" };
set.Permutations().ForEach((x,index) => {
    Console.WriteLine($"第{index 1}种排列组合");
    x.ForEach(y => { Console.WriteLine(y); });
});

//组合 Subsets
var set = new[] { "a", "b", "c" }.Subsets();
set.ForEach((x, index) => {
    Console.WriteLine($"第{index   1}种组合");
    x.ForEach(y => { Console.WriteLine(y); });
});

八、BatchExtension (每批次数量) 分批; PartitionExtension 分区按条件分区

//第一批 1,2,3 第二批4,5,6 第三批7,8,9
new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 }.Batch(3).ForEach((x,index) => {
    Console.WriteLine($"第{index 1}批");
    x.ForEach(y => {
        Console.WriteLine(y);
    });
});

//True 0,2,4,6,8 False 1,3,5,7,9
var result = Enumerable.Range(0, 10)
                .Partition(x => x % 2 == 0);

result.False.ForEach(x=> {
    Console.WriteLine(x);
});

九、StartsWithExtension; EndsWithExtension;

var result1 = new string[] { "a", "b", "c" }.StartsWith(new string[] { "a", "b" }); //true
var result2 = new string[] { "a", "b", "c" }.EndsWith(new string[] { "b", "c" }); //true

十、Evaluate 解方程式、运算

var factories = new Func<int>[]
{
    () => -2,
    () => 4 1,
    () => int.MaxValue,
    () => int.MinValue,
};
var results = factories.Evaluate();
results.ForEach(x => Console.WriteLine(x));

十一、FillForwardExtension 向前填充，FillBackwardExtension 向后填充

//FillForward 如果有空值，取左边第一个有效值
//FillBackward 如果有空值，取右边第一个有效值
int? na = null;
var input = new[] { na, 1, 2, na, 3, 4, na };
var result1 = input.FillForward();
var result2 = input.FillBackward();
result1.ForEach(x => Console.WriteLine(x)); //"",1,2,2,3,4,4
result2.ForEach(x => Console.WriteLine(x)); //1,1,2,3,3,4,""

十二、IndexExtension 加上下标，形成一个新的键值对

const string one = "one";
const string two = "two";
const string three = "three";
var result = new[] { one, two, three }.Index();
result.ForEach(x => { Console.WriteLine(x); }); //[0,"one"]

十三、PadExtension 从后面填充，PadStartExtension 从前面填充

var result1 = new[] { 123, 456, 789 }.Pad(4); //123,456,789,0
var result2 = new[] { 123, 456, 789 }.PadStart(4); //0,123,456,789

十四、PairwiseExtension 按规则结队

var result = new[] { "a", "b", "c", "d" }.Pairwise((x, y) => x   y); //ab,bc,cd

十五、RandomSubsetExtension 随机取N个数据生成子集

Enumerable.Range(1, 10).RandomSubset(4, new Random())
    .ForEach(x => { Console.WriteLine(x); });

十六、SliceExtension;截取一段序列

Enumerable.Range(1, 100).Slice(10, 10);//11,12,13...20

参考：

MoreLinq开源地址
https://github.com/morelinq/MoreLINQ

MoreLinq示例
https://gitee.com/gsbhz/MoreLINQ

Linq扩展之MoreLinq

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