Lambda 表达式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyLambda.Extend
{
    /// <summary>
    /// 扩展方法:静态类 静态方法  第一个参数类型前面加上this
    /// ExtendShow.ToInt(ivalue);换成 ivalue.ToInt()
    /// 
    /// 
    /// </summary>
    public static class ExtendShow
    {
        public static int ToInt(this int? iParameter)
        {
            return iParameter ?? 0;
        }

        public static void NoShow(this LambdaShow show)
        {
            Console.WriteLine("这里是扩展的 NoShow");
        }

        public static void Show(this LambdaShow show)
        {
            Console.WriteLine("这里是扩展的 NoShow");
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="object"></param>
        /// <returns></returns>
        public static DateTime ToDateTime(this object @object, int a)
        {
            return DateTime.Now;
        }

        public static DateTime Execute(this Action act)
        {
            act();
            return DateTime.Now;
        }

        public static IEnumerable<TSource> ElevenWhere<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> func)
        {
            List<TSource> studentList = new List<TSource>();
            foreach (TSource item in source)
            {
                bool bResult=func.Invoke(item);
                if (bResult)
                {
                    studentList.Add(item);
                }
            }
            return studentList;
        }


    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyLambda
{
    public delegate void NoReturnNoParaOutClass();
    public delegate void Action<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, in T17>
    (T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16, T17 arg17);

    public class LambdaShow
    {
        public delegate void NoReturnNoPara();//1 委托的声明
        public delegate int WithReturnNoPara();
        public delegate void NoReturnWithPara(int id, string name);
        public delegate LambdaShow WithReturnWithPara(DateTime time);

        public void Show()
        {
            string nameOut = "糯米飞机";
            {
                Student student = new Student();
                student.Id = 1;
                student.Name = "打兔子的猎人";
                student.Age = 27;
                student.ClassId = 2;

                student.Study();
            }
            {
                Student student = new Student()
                {
                    Id = 1,
                    Name = "打兔子的猎人",
                    Age = 27,
                    ClassId = 2
                };
                student.Study();
            }
            {
                NoReturnWithPara method = new NoReturnWithPara(this.DoNothing);//2 委托的实例化
                method.Invoke(1, "Gain");//3 委托的调用
            }
            {
                NoReturnWithPara method = this.DoNothing;
                method.Invoke(2, "憨豆");
            }

            {
                NoReturnWithPara method = new NoReturnWithPara(
                    delegate(int id, string name)
                    {
                        Console.WriteLine(nameOut);
                        Console.WriteLine("{0} {1} DoNothing");
                    });
                method.Invoke(3, "yoyo");
            }
            {
                NoReturnWithPara method = new NoReturnWithPara(
                                  (int id, string name) =>//goes to
                                  //lambda表达式：是一个匿名方法，是一个方法
                                  {
                                      Console.WriteLine(nameOut);
                                      Console.WriteLine("{0} {1} DoNothing");
                                  });
                method.Invoke(4, "Nine");
            }
            {
                NoReturnWithPara method = new NoReturnWithPara(
                                     (id, name) =>
                                     //去掉参数类型，原因是委托的约束
                                     {
                                         Console.WriteLine("{0} {1} DoNothing");
                                     });
                method.Invoke(5, "小昶");
            }
            {
                //如果方法体只有一行，那么可以去掉大括号和分号,多行不行
                //如果参数只有一个  可以去掉小括号
                //如果没有参数，直接用小括号

                NoReturnWithPara method = new NoReturnWithPara((id, name) => Console.WriteLine("{0} {1} DoNothing", id, name));
                method.Invoke(6, "梦醒时分");
            }
            {
                NoReturnWithPara method = (id, name) => Console.WriteLine("{0} {1} DoNothing", id, name);
                method.Invoke(7, "小石头");
                method(8, "Y");
            }

            {
                //0到16个参数  无返回值的委托
                Action act1 = () => Console.WriteLine("1234");
                Action<int> act2 = t => { };
                Action<int, NoReturnWithPara, LambdaShow, LambdaShow, string, string, string, string, string, string, string, string, string, string, string, string> act3 = null;
                Action<int, NoReturnWithPara, NoReturnWithPara, LambdaShow, LambdaShow, string, string, string, string, string, string, string, string, string, string, string, string> act4 = null;
            }
            {
                //0到16个参数  带返回值的委托
                Func<int> func1 = () => 1;
                int i = func1();

                Func<int, string> func2 = t => "1234";
                Func<int, int, NoReturnWithPara, LambdaShow, LambdaShow, string, string, string, string, string, string, string, string, string, string, string, string> func3 = null;
            }
            {
                //多返回值：1 返回对象  2  ref out
                WithReturnWithParaRefOut method = new WithReturnWithParaRefOut(
                    delegate(ref DateTime time, out int i)
                    {
                        i = 1;
                        return this;
                    });//lambda表达式不行
            }
        }


        public delegate LambdaShow WithReturnWithParaRefOut(ref DateTime time, out int i);


        private void DoNothing(int id, string name)
        {
            Console.WriteLine("{0} {1} DoNothing out");
        }

        private void DoNothing1()
        {
            Console.WriteLine("DoNothing");
        }

        private void DoNothing2()
        {
            Console.WriteLine("DoNothing");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MyLambda.Extend;

namespace MyLambda
{
    public class LinqShow
    {

        private List<Student> GetStudentList()
        {
            #region 初始化数据
            List<Student> studentList = new List<Student>()
            {
                new Student()
                {
                    Id=1,
                    Name="打兔子的猎人",
                    ClassId=2,
                    Age=35
                },
                new Student()
                {
                    Id=1,
                    Name="Alpha Go",
                    ClassId=2,
                    Age=23
                },
                 new Student()
                {
                    Id=1,
                    Name="白开水",
                    ClassId=2,
                    Age=27
                },
                 new Student()
                {
                    Id=1,
                    Name="狼牙道",
                    ClassId=2,
                    Age=26
                },
                new Student()
                {
                    Id=1,
                    Name="Nine",
                    ClassId=2,
                    Age=25
                },
                new Student()
                {
                    Id=1,
                    Name="Y",
                    ClassId=2,
                    Age=24
                },
                new Student()
                {
                    Id=1,
                    Name="小昶",
                    ClassId=2,
                    Age=21
                },
                 new Student()
                {
                    Id=1,
                    Name="yoyo",
                    ClassId=2,
                    Age=22
                },
                 new Student()
                {
                    Id=1,
                    Name="冰亮",
                    ClassId=2,
                    Age=34
                },
                 new Student()
                {
                    Id=1,
                    Name="瀚",
                    ClassId=2,
                    Age=30
                },
                new Student()
                {
                    Id=1,
                    Name="毕帆",
                    ClassId=2,
                    Age=30
                },
                new Student()
                {
                    Id=1,
                    Name="一点半",
                    ClassId=2,
                    Age=30
                },
                new Student()
                {
                    Id=1,
                    Name="小石头",
                    ClassId=2,
                    Age=28
                },
                new Student()
                {
                    Id=1,
                    Name="大海",
                    ClassId=2,
                    Age=30
                },
            };
            #endregion
            return studentList;
        }


        public void Show()
        {
            List<Student> studentList = this.GetStudentList();

            List<Student> studentListlessThan30 = new List<Student>();
            foreach (var item in studentList)
            {
                if (item.Age < 30)
                {
                    studentListlessThan30.Add(item);
                }
            }



            {
                var list = studentList.Where<Student>(s => s.Age < 30);//陈述句
                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.Name, item.Age);
                }
            }
            {
                Console.WriteLine("********************");
                var list = studentList.ElevenWhere<Student>(s => s.Age < 30);//陈述句

                //Func<Student, bool> func = new Func<Student, bool>(s => s.Age < 30);
                //var list = ExtendShow.ElevenWhere<Student>(studentList,func);//陈述句
                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.Name, item.Age);
                }
            }
            {
                Console.WriteLine("********************");
                var list = from s in studentList
                           where s.Age < 30
                           select s;

                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.Name, item.Age);
                }
            }


            {
                Console.WriteLine("********************");
                var list = studentList.Where<Student>(s => s.Age < 30)
                                     .Select(s => new
                                     {
                                         IdName = s.Id + s.Name,
                                         ClassName = s.ClassId == 2 ? "高级班" : "其他班"
                                     });
                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.ClassName, item.IdName);
                }
            }
            {
                Console.WriteLine("********************");
                var list = from s in studentList
                           where s.Age < 30
                           select new
                           {
                               IdName = s.Id + s.Name,
                               ClassName = s.ClassId == 2 ? "高级班" : "其他班"
                           };

                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.ClassName, item.IdName);
                }
            }
            {
                Console.WriteLine("********************");
                var list = studentList.Where<Student>(s => s.Age < 30)
                                     .Select(s => new
                                     {
                                         Id = s.Id,
                                         ClassId = s.ClassId,
                                         IdName = s.Id + s.Name,
                                         ClassName = s.ClassId == 2 ? "高级班" : "其他班"
                                     })
                                     .OrderBy(s => s.Id)
                                     .OrderByDescending(s => s.ClassId)
                                     .Skip(2)
                                     .Take(3)
                                     ;
                foreach (var item in list)
                {
                    Console.WriteLine("Name={0}  Age={1}", item.ClassName, item.IdName);
                }
            }
            {
                List<Class> classList = new List<Class>()
                {
                    new Class()
                    {
                        Id=1,
                        ClassName="初级班"
                    },
                    new Class()
                    {
                        Id=2,
                        ClassName="高级班"
                    },
                    new Class()
                    {
                        Id=3,
                        ClassName="微信小程序"
                    },
                };

                var list = from s in studentList
                           join c in classList on s.ClassId equals c.Id
                           select new
                           {
                               Name = s.Name,
                               CalssName = c.ClassName
                           };
            }

        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyLambda
{
    public class Student
    {
        public int Id { get; set; }
        public int ClassId { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }

        public void Study()
        {
            Console.WriteLine("{0} {1}跟着Eleven老师学习.net高级开发", this.Id, this.Name);
        }
    }

    public class Class
    {
        public int Id { get; set; }
        public string ClassName { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MyLambda.Extend;

namespace MyLambda
{
    /// <summary>
    /// 1 委托简介
    /// 2 匿名方法 匿名类 var
    /// 3 lambda表达式 goes to
    /// 4 系统自带委托Action/Func
    /// 5 扩展方法
    /// 6 linq扩展  
    /// 7 linq简单回顾
    /// 8 作业部署
    /// </summary>
    class Program
    {
        //private var name = "";
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("=============================今天是lambda/linq课程=========================================");
                {
                    LambdaShow show = new LambdaShow();
                    show.Show();

                    show.NoShow();
                    show.ToDateTime(1);
                }
                #region MyRegion


                {
                    var model = new
                    {
                        Id = 1,
                        Name = "Alpha Go",
                        Age = 21,
                        ClassId = 2
                    };
                    Console.WriteLine(model.Id);
                    Console.WriteLine(model.Name);
                    //model.Name = "张伟东";

                    Student student = new Student()
                    {
                        Id = 1,
                        Name = "打兔子的猎人",
                        Age = 27,
                        ClassId = 2
                    };

                    var name = "";
                    Console.WriteLine(name);

                    //var id;
                }
                #endregion

                #region MyRegion


                {
                    int? ivalue = null;
                    int? ivalue2 = 1;

                    ivalue.ToDateTime(1);
                    ivalue2.ToDateTime(1);

                    int i = ExtendShow.ToInt(ivalue);


                    int i2 = ivalue.ToInt();

                    new Action(() => { }).Execute();
                }
                #endregion

                #region linq
                {
                    LinqShow show = new LinqShow();
                    show.Show();
                }
                #endregion
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.Read();
        }
    }
}