Linq 入门系列 [Group,Distinct,Union,Concat,Intersect,Except篇]

 /**/////////////////////////////
    ///以下是Group,Distinct,Union,Concat,Intersect,Except的例子和解释
    /////////////////////////////
    class Program
    {
        DB#region DB

        private static List<Student> GetStudents()
        {
            List<Student> students = new List<Student> { 
             new Student{ Name="YOUNG", Age=25, Language="Chinese"},
             new Student{ Name="JESSIE", Age=21, Language="Scotland"},
             new Student{ Name="KELLY", Age=18, Language="English"},
             new Student{ Name="JUNE", Age=20, Language="Chinese"},
             new Student{ Name="ADRIAN", Age=22, Language="Italy"},
             new Student{ Name="BRUCE", Age=17, Language="Scotland"},
             new Student{ Name="BRANT", Age=30, Language="Germany"},
             new Student{ Name="BEN", Age=25, Language="Chinese"}
             };
            return students;
        }

        #endregion

        static void Main(string[] args)
        {
            List<Student> studentList = GetStudents();

            //Group(studentList);

            //Distinct(studentList);

            //Union(studentList);

            //Concat(studentList);

            Intersect(studentList);

            //Except();
        }

        Group,Distinct,Union,Concat,Intersect,Except#region Group,Distinct,Union,Concat,Intersect,Except

        private static void Group<T>(T obj)
        {
            UsingGroupToCollectGrouping(obj);

            //<hr>用group将集合体分组：<br>
            //<div class='result'>Language:Chinese</div>
            //<div class='result'>——YOUNG</div>
            //<div class='result'>——JUNE</div>
            //<div class='result'>——BEN</div>
            //<div class='result'>Language:Scotland</div>
            //<div class='result'>——JESSIE</div>
            //<div class='result'>——BRUCE</div>
            //<div class='result'>Language:English</div>
            //<div class='result'>——KELLY</div>
            //<div class='result'>Language:Italy</div>
            //<div class='result'>——ADRIAN</div>
            //<div class='result'>Language:Germany</div>
            //<div class='result'>——BRANT</div>
        }

        private static void UsingGroupToCollectGrouping<T>(T obj)
        {
            Console.WriteLine("<hr>用group将集合体分组：<br>");
            var stu = from student in RevealChangeType(obj)
                      group student by student.Language into studentsgroup
                      select new { lang = studentsgroup.Key, member = studentsgroup };

            foreach (var g in stu)
            {
                Console.WriteLine(string.Format("<div class='result'>Language:{0}</div>", g.lang));
                foreach (var student in g.member)
                {
                    Console.WriteLine(string.Format("<div class='result'>——{0}</div>", student.Name));
                }
            }
        }

        private static void Distinct<T>(T obj)
        {
            UsingDistinctFilterSame(obj);

            //<hr>用Distinct将过滤相同项：<br>
            //<span class='result'>Chinese</span>
            //<span class='result'>Scotland</span>
            //<span class='result'>English</span>
            //<span class='result'>Italy</span>
            //<span class='result'>Germany</span>
        }

        private static void UsingDistinctFilterSame<T>(T obj)
        {
            Console.WriteLine("<hr>用Distinct将过滤相同项：<br>");
            var lang = (from stu in RevealChangeType(obj)
                        select stu.Language).Distinct();

            foreach (var l in lang)
            {
                Console.WriteLine(string.Format("<span class='result'>{0}</span>", l));
            }
        }

        private static void Union<T>(T obj)
        {
            Console.WriteLine("<hr>用Union连接不同集合体：<br>");

            string[] stringArray = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis", "Chinese" };

            var lang = (from stu in RevealChangeType(obj)
                        select stu.Language).Union(stringArray);

            //Union会自动过滤各集合体中的相同项，无需Distinct
            foreach (var l in lang)
            {
                Console.WriteLine(string.Format("<span class='result'>{0}</span>", l));
            }
        }

        private static void Concat<T>(T obj)
        {
            Console.WriteLine("<hr>用Concat连接不同集合体：<br>");

            string[] stringArray = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis", "Chinese" };

            var lang = (from stu in RevealChangeType(obj)
                        select stu.Language).Concat(stringArray);

            //Concat不会自动过滤各集合体中的相同项
            foreach (var l in lang)
            {
                Console.WriteLine(string.Format("<span class='result'>{0}</span>", l));
            }

        }

        private static void Intersect<T>(T obj)
        {
            Console.WriteLine("<hr>用Intersect取不同集合体的相同项(交集)：<br>");

            string[] Book1Array1 = { "Csharp", "Javascript", "FrameWork", "Use Compute", "WebDesign" };
            string[] Book1Array2 = { "Chanese", "English", "Use Compute", "Business", "WebDesign" };

            //var books = Book1Array1.Intersect(Book1Array1);
            //<hr>用Intersect取不同集合体的相同项(交集)：<br>
            //<span class='result'>Csharp</span>
            //<span class='result'>Javascript</span>
            //<span class='result'>FrameWork</span>
            //<span class='result'>Use Compute</span>
            //<span class='result'>WebDesign</span>

            var books = Book1Array .Intersect(Book1Array2);
            //<hr>用Intersect取不同集合体的相同项(交集)：<br>
            //<span class='result'>Use Compute</span>
            //<span class='result'>WebDesign</span>;

            foreach (var book in books)
            {
                Console.WriteLine(string.Format("<span class='result'>{0}</span>", book));
            }
        }

        private static void Except()
        {
            string[] Book1Array1 = { "Csharp", "Javascript", "FrameWork", "Use Compute", "WebDesign" };
            string[] Book1Array2 = { "Chanese", "English", "Use Compute", "Business", "WebDesign" };

            Console.WriteLine("<hr>用Except从集合体中排出和另一个集合体相同的项：<br>");
            var Books2 = Book1Array1.Except(Book1Array2);
            foreach (var book in Books2)
            {
                Console.WriteLine(string.Format("<span class='result'>{0}</span>", book));
            }
        }

        #endregion

        private static IEnumerable<Student> RevealChangeType<T>(T obj)
        {
            IEnumerable<Student> student = obj as IEnumerable<Student>;

            return student;
        }
    }

    sealed class Student
    {
        public int age;
        public int Age
        {
            get { return age; }
            set { age = value; }
        }

        private string name;
        public string Name
        {
            get { return name; }
            set { name = value; }
        }

        private string language;
        public string Language
        {
            get { return language; }
            set { language = value; }
        }
    }