LINQ 学习路程 -- 查询操作 Average Count Max Sum

IList<int> intList = new List<int>>() { , ,  };

var avg = intList.Average();

Console.WriteLine("Average: {0}", avg);

IList<Student> studentList = new List<Student>>() {
        new Student() { StudentID = , StudentName = "John", Age = } ,
        new Student() { StudentID = , StudentName = "Moin",  Age =  } ,
        new Student() { StudentID = , StudentName = "Bill",  Age =  } ,
        new Student() { StudentID = , StudentName = "Ram" , Age = } ,
        new Student() { StudentID = , StudentName = "Ron" , Age =  }
    };

var avgAge = studentList.Average(s => s.Age);

Console.WriteLine("Average Age of Student: {0}", avgAge);

var totalAge = (from s in studentList
                select s.age).Count(); 

int Count<TSource>();

int Count<TSource>(Func<TSource, bool> predicate);

IList<Student> studentList = new List<Student>>() {
        new Student() { StudentID = , StudentName = "John", Age = } ,
        new Student() { StudentID = , StudentName = "Moin",  Age =  } ,
        new Student() { StudentID = , StudentName = "Bill",  Age =  } ,
        new Student() { StudentID = , StudentName = "Ram" , Age = } ,
        new Student() { StudentID = , StudentName = "Mathew" , Age =  }
    };

var numOfStudents = studentList.Count();

Console.WriteLine("Number of Students: {0}", numOfStudents);

// Student collection
IList<Student> studentList = new List<Student>>() {
        new Student() { StudentID = , StudentName = "John", Age = } ,
        new Student() { StudentID = , StudentName = "Moin",  Age =  } ,
        new Student() { StudentID = , StudentName = "Bill",  Age =  } ,
        new Student() { StudentID = , StudentName = "Ram" , Age = } ,
        new Student() { StudentID = , StudentName = "Mathew" , Age =  }
    };

var numOfStudents = studentList.Count(s => s.Age >= );

Console.WriteLine("Number of Students: {0}", numOfStudents);

IList<int> intList = new List<int>() { , , , , ,  };

var largest = intList.Max();

Console.WriteLine("Largest Element: {0}", largest);

var largestEvenElements = intList.Max(i => {
                                    if(i% == )
                                        return i;

                                    return ;
                                });

Console.WriteLine("Largest Even Element: {0}", largestEvenElements );

IList<Student> studentList = new List<Student>>() {
        new Student() { StudentID = , StudentName = "John", Age = } ,
        new Student() { StudentID = , StudentName = "Moin",  Age =  } ,
        new Student() { StudentID = , StudentName = "Bill",  Age =  } ,
        new Student() { StudentID = , StudentName = "Ram" , Age = } ,
        new Student() { StudentID = , StudentName = "Ron" , Age =  }
    };

var oldest = studentList.Max(s => s.Age);

Console.WriteLine("Oldest Student Age: {0}", oldest);

public class Student : IComparable<Student>
{
    public int StudentID { get; set; }
    public string StudentName { get; set; }
    public int Age { get; set; }
    public int StandardID { get; set; }

    public int CompareTo(Student other)
    {
        if (this.StudentName.Length >= other.StudentName.Length)
            return ;

        return ;
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Student collection
        IList<Student> studentList = new List<Student>>() {
                new Student() { StudentID = 1, StudentName = "John", Age = 13} ,
                new Student() { StudentID = 2, StudentName = "Moin",  Age = 21 } ,
                new Student() { StudentID = 3, StudentName = "Bill",  Age = 18 } ,
                new Student() { StudentID = 4, StudentName = "Ram" , Age = 20} ,
                new Student() { StudentID = 5, StudentName = "Steve" , Age = 15 }
            };

        var studentWithLongName = studentList.Max();

        Console.WriteLine("Student ID: {0}, Student Name: {1}",
                                        .StudentID, studentWithLongName.StudentName)
    }
}

IList<int> intList = new List<int>() { , , , , ,  };

var total = intList.Sum();

Console.WriteLine("Sum: {0}", total);

var sumOfEvenElements = intList.Sum(i => {
                                    if(i% == )
                                        return i;

                                    return ;
                                });

Console.WriteLine("Sum of Even Elements: {0}", sumOfEvenElements );

IList<Student> studentList = new List<Student>>() {
        new Student() { StudentID = , StudentName = "John", Age = } ,
        new Student() { StudentID = , StudentName = "Moin",  Age =  } ,
        new Student() { StudentID = , StudentName = "Bill",  Age =  } ,
        new Student() { StudentID = , StudentName = "Ram" , Age = } ,
        new Student() { StudentID = , StudentName = "Ron" , Age =  }
    };

var sumOfAge = studentList.Sum(s => s.Age);

Console.WriteLine("Sum of all student's age: {0}", sumOfAge);

var numOfAdults = studentList.Sum(s => {

    if(s.Age >= )
        return ;
    else
        return ;
});

Console.WriteLine("Total Adult Students: {0}", numOfAdults);