static void Main(string[] args)
{
string[] words = { "zero", "one", "two", "three", "four" };
int[] numbers = { 0, 1, 2, 3, 4 };
string[] names = { "Robin", "Ruth", "Bob", "Emma" };
string[] colors = { "Red", "Blue", "Beige", "Green" };
string[] abbc = { "a", "b", "b", "c" };
string[] cd = { "c", "d" };
#region 聚合 立即执行
//Console.WriteLine(numbers.Sum());//10
//Console.WriteLine(numbers.Count());//5
//Console.WriteLine(numbers.Average());//2
//Console.WriteLine(numbers.LongCount(c => c % 2 == 0));//3
//Console.WriteLine(words.Min(word => word.Length));//3
//Console.WriteLine(words.Max(word => word.Length));//5
//Console.WriteLine(numbers.Aggregate("seed", (current, item) => current + item, result => result.ToUpper()));//SEED01234
#endregion
#region 连接 延迟执行 流式数据
//var result = numbers.Concat(new int[] { 5, 6, 7, 8, 9 });
//foreach (var i in result)
//{
// Console.WriteLine(i);//0,1,2,3,4,5,6,7,8,9
//}
#endregion
#region 转换
object[] allStrings = { "these", "are", "all", "strings" };
object[] notAllStrings = { "number", "at", "the", "end", 5 };
////延迟执行 流式数据
////allStrings.Cast<string>();//强转,生成 IEnumerable<string> "these", "are", "all", "strings",转换失败则抛出异常
////allStrings.OfType<string>();//尝试转换,生成 IEnumerable<string> "these", "are", "all", "strings", 过滤掉转换失败的元素
////notAllStrings.Cast<string>();
////notAllStrings.OfType<string>();
////立即执行
//numbers.ToArray();
//numbers.ToList();
//words.ToDictionary(s => s.Substring(0, 2)).Print();//[ze,zero],[on,one]....
//var result = words.ToLookup(word => word[0]);
///*
// * z:zero
// * o:one
// * t:two,three
// * f:four
// *
// */
//foreach (var item in result)
//{
// Console.WriteLine(item.Key);
// foreach (var s in item)
// {
// Console.WriteLine("--" + s);
// }
//}
////words.ToDictionary(word => word[0]);//抛出异常,每个键只能有一个元素,所以在遇到"t"时转换失败
#endregion
#region 元素操作符 立即执行
//Console.WriteLine(words.ElementAt(2));
//Console.WriteLine(words.ElementAtOrDefault(10));
//words.First();
//words.First(f => f.Length == 3);
//words.FirstOrDefault(f => f.Length > 10);
//words.Last();
//words.Single();
////...
#endregion
#region 相等操作符 立即执行
//var b1 = words.SequenceEqual(new string[] { "zero", "one", "two", "three", "four" });//true
//var b2 = words.SequenceEqual(new string[] { "ZERO", "one", "Two", "three", "four" });//false
//var b3 = words.SequenceEqual(new string[] { "Zero", "one", "Two", "three", "four" }, StringComparer.OrdinalIgnoreCase);//true
//Console.WriteLine($"{b1},{b2},{b3}");
#endregion
#region 生成 延迟执行 流式处理
//numbers.DefaultIfEmpty();//{ 0, 1, 2, 3, 4 }
//new int[0].DefaultIfEmpty();//{0}
//new int[0].DefaultIfEmpty(100);//{100}
//Enumerable.Range(0, 9);//{0,1,2,3,4,5,6,7,8}
//Enumerable.Repeat(99, 3);//{99,99,99}
//Enumerable.Empty<int>();//一个类型为 IEnumerable<int> 的空序列
#endregion
#region 分组 延迟执行 缓存数据 当迭代分组的结果序列时,消费的是整个输入序列
//ToLookup算是其中一个
//words.GroupBy(word => word.Length);
//var result = words.GroupBy(word => word.Length, word => word.ToUpper());
/*
* 4:ZERO,FOUR
* 3:ONE,TWO
* 5:THREE
*/
//foreach (var item in result)
//{
// Console.WriteLine(item.Key+":");
// item.Print();
//}
//var result = words.GroupBy(word => word.Length, (key, g) => key + ":" + g.Count());
//foreach (var item in result)
//{
// item.Print();//4:2,3:2,5:1
//}
#endregion
#region 连接 延迟执行,流式处理左边序列,对于右边序列,在请求第一个结果时变读取其全部内容
//names.Join(colors, left => left[0], right => right[0], (left, right) => left + ":" + right).Print();
//Console.WriteLine("**************");
//names.GroupJoin(colors, left => left[0], right => right[0], (left, right) => left + ":" + string.Join(",", right)).Print();
#endregion
#region 分部 延迟执行 流式处理
//words.Skip(1).Take(2);
//words.TakeWhile(word => word.Length <= 4);
//words.SkipWhile(word => word.Length <= 4);
#endregion
#region 投影 延迟执行
//words.Select(word => word.Length);
//index 表示当前元素在原序列中的索引
//words.Select((word, index) => index + ":" + word).Print();//0:zero,1:one,2:two...
//将序列中的每个元素都投影到一个新的序列中
//words.SelectMany(word => word.ToArray()).Print();//z,e,r,o,o,n,e,t,w,o,t,h,r,e,e,,f,o,u,r
/*
* one
* two
* two
* three
* three
* three
* four
* four
* four
* four
*
*/
//words.SelectMany((word, index) => Enumerable.Repeat(word, index)).Print();
//投影顺序:先是每个序列的第一个元素,接着是每个序列的第二个元素,直到任意一个源序列到达末尾,结果序列都将停止生成
//names.Zip(colors.Take(3), (left, right) => left + ":" + right).Print();
#endregion
#region 数量 立即执行
words.All(word => word.Length > 2);//true
words.All(word => word.Length > 6);//false
words.Any();//true
words.Any(word => word.Length == 6);//false
words.Contains("ONE", StringComparer.OrdinalIgnoreCase);//true
#endregion
#region 过滤 延迟执行 流式数据
//OfType 也算过滤
//words.Where(word => word.Length > 3);
//words.Where((word, index) => index < word.Length).Print();//four 的索引是 4,长度是 4,所以不会打印出来
#endregion
#region 基于集的操作符 延迟执行
//流式处理
//abbc.Distinct().Print();//a,b,c
//四种操作都有该方式的重载
abbc.Distinct(StringComparer.OrdinalIgnoreCase).Print();//a,b,c
//abbc.Union(cd).Print();//a,b,c,d
//左序列流式处理,有序列缓存处理
//abbc.Intersect(cd).Print();//c
//abbc.Except(cd).Print();//a,b
#endregion
#region 排序 延迟执行 缓存处理
words.OrderBy(word => word.Length);
words.OrderByDescending(word => word.Length);
words.OrderBy(word => word.Length).ThenBy(word => word);
words.Reverse();
#endregion
Console.ReadKey();
}
