C#Linq 基本操作实例
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using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace First_exam{ class Student { /// <summary> ///学生姓名的字段和属性 /// </summary> private string _Name; public string Name { get { return this._Name; } } private string _Xingbie; /// <summary> /// 学生性别的字段和属性 /// </summary> public string Xingbie { get { return this._Xingbie; } } /// <summary> /// 学生年龄的字段和属性 /// </summary> private uint _Age; public uint Age { get { return this._Age; } } /// <summary> /// 学生成绩的字段和属性 /// </summary> private List<LessonScore> _Scores; public List<LessonScore> Scores { get { return this._Scores; } } /// <summary> /// 构造函数，传入学生姓名，性别，年龄，成绩 /// </summary> public Student(string name, string xb, uint age, List<LessonScore> scrs) { this._Name = name; this._Xingbie = xb; this._Age = age; this._Scores = scrs; } public Student(string name, string xb, uint age) { this._Name = name; this._Xingbie = xb; this._Age = age; this._Scores = null; } public override string ToString() { string str; str = string.Format("{0}--{1}--{2}",this._Name, this._Age,this._Xingbie); return str; } } class LessonScore { /// <summary> /// 课程成绩的字段和属性 /// </summary> private float _Score; public float Score { get { return this._Score; } } /// <summary> /// 课程名称的字段和属性 /// </summary> private string _Lessson; public string Lesson { get { return this._Lessson; } } /// <summary> /// 构造函数 /// </summary> public LessonScore(string les, float scr) { this._Lessson = les; this._Score = scr; } public override string ToString() { string str; str = string.Format("{0}----{1}分", this._Lessson,this._Score); return str; } } class Program { static void Main(string[] args) { Student[] arr = { new Student("张氏那","男",20), new Student("李四","男",23), new Student("李霞","女",23), new Student("王妈妈","女",25), new Student("郭明","男",22), new Student("欧阳夏","女",24), new Student("王丹","女",20), new Student("张宝","男",25), }; var query = from val in arr select val; foreach (Student item in query) { Console.WriteLine(item); } Console.WriteLine(); var query2 = from val in arr select val.Name; foreach(string item in query2) { Console.Write("{0}, ",item); } Console.WriteLine(); Console.WriteLine(); var query3 = from val in arr select val.Name.Length; foreach (int item in query3) { Console.Write("{0}, ", item); } Console.WriteLine(); Console.WriteLine(); var query4 = from val in arr select new { val.Name, val.Age, NameLen = val.Name.Length}; foreach(var item2 in query4) { Console.WriteLine(item2); } Console.WriteLine(); int[] ary = { 9,54,32,1,67,43,0,9,7,4,9,2,23,66,61}; var query5 = from val in ary orderby val select val; foreach(var item in query5) { Console.Write("{0} ",item); } Console.WriteLine(); Console.WriteLine(); var query6 = from val in ary orderby val descending select val; foreach (var item in query6) { Console.Write("{0} ", item); } Console.WriteLine(); Console.WriteLine(); var query7 = from val in arr orderby val.Name.Length ascending, val.Age descending select val; foreach(var item in query7) { Console.WriteLine(item); } Console.WriteLine(); var query8 = from val in arr group val by val.Xingbie; foreach(var grp in query8) { Console.WriteLine(grp.Key); foreach(var st in grp) { Console.WriteLine("\t{0}",st); } } Console.WriteLine(); var query9 = from val in arr group val by val.Age into stgrp orderby stgrp.Key descending select stgrp; foreach(var st in query9) { Console.WriteLine("{0}岁的学生：",st.Key); foreach(var stu in st) { Console.WriteLine("\t{0}",stu); } } Console.WriteLine(); Console.WriteLine("**************************************************************************"); Console.WriteLine(); /* *from子句的复合查询 */ Student[] stAry = { new Student("张氏那","男",20, new List<LessonScore>{ new LessonScore("语文",80.5f), new LessonScore("数学",90f), new LessonScore("英语",89f) }), new Student("李四","男",23, new List<LessonScore>{ new LessonScore("语文",86.5f), new LessonScore("数学",97f), new LessonScore("英语",95f) }), new Student("李霞","女",23, new List<LessonScore>{ new LessonScore("语文",76f), new LessonScore("数学",85f), new LessonScore("英语",79f) }), new Student("王妈妈","女",25, new List<LessonScore>{ new LessonScore("语文",85f), new LessonScore("数学",87f), new LessonScore("英语",79f) }), new Student("郭明","男",22, new List<LessonScore>{ new LessonScore("语文",69f), new LessonScore("数学",72f), new LessonScore("英语",83f) }), new Student("欧阳夏","女",24, new List<LessonScore>{ new LessonScore("语文",85f), new LessonScore("数学",85f), new LessonScore("英语",79f) }), new Student("王丹","女",20, new List<LessonScore>{ new LessonScore("语文",73f), new LessonScore("数学",77f), new LessonScore("英语",80f) }), new Student("张宝","男",25, new List<LessonScore>{ new LessonScore("语文",88f), new LessonScore("数学",89f), new LessonScore("英语",94f) }), }; var query10 = from st in stAry from scr in st.Scores where scr.Score > 80 group new { st.Name, scr } by st.Name; foreach(var grp in query10) { Console.WriteLine(grp.Key); foreach(var item in grp) { Console.WriteLine("\t{0}",item); } } Console.WriteLine(); Console.WriteLine("**************************************************************************"); Console.WriteLine(); int[] intarry1 = { 5,10,15,20,25,50,30,33,100}; int[] intarry2 = { 10,20,30,40,50,60,70,80,90,100}; var query11 = from val1 in intarry1 from val2 in intarry2 where val2 % val1 == 0 group val2 by val1; foreach(var grp in query11) { Console.Write("{0}: ",grp.Key); foreach(var val in grp) { Console.Write("{0} ",val); } Console.WriteLine(); } Console.WriteLine(); Console.WriteLine("*********************join*****************************************"); Console.WriteLine(); Console.WriteLine("**********内部联接**************************"); int[] intarray1 = { 5,15,25,30,33,40}; int[] intarray2 = { 10,20,30,40,50,60,70,80,90,100}; var query12 = from val1 in intarray1 join val2 in intarray2 on val1 % 5 equals val2 % 15 select new { VAL1 = val1,VAL2 = val2}; foreach(var val in query12) { Console.WriteLine(val); } Console.WriteLine(); Console.WriteLine("**********分组联接**************************"); var query13 = from val1 in intarray1 join val2 in intarray2 on val1 % 5 equals val2 % 15 into grpName select new { VAL1 = val1, VAL2 = grpName}; foreach(var val in query13) { Console.Write("{0}: ",val.VAL1); foreach(var obj in val.VAL2) { Console.Write("{0} ",obj); } Console.WriteLine(); } Console.WriteLine(); Console.WriteLine("**********左外部联接**************************"); var query14 = from val1 in intarray1 join val2 in intarray2 on val1 % 5 equals val2 % 15 into grpName from grp in grpName.DefaultIfEmpty() select new { VAL1 = val1 , VAL2 = grp}; foreach(var val in query14) { Console.WriteLine(val); } } }} 阅读全文
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