ICollection和IEnumerable之间有一些基本的区别

IEnumerable -仅包含获取枚举器的GetEnumerator方法，并允许循环 ICollection包含其他方法:添加，删除，包含，计数，CopyTo ICollection继承自IEnumerable 使用ICollection，您可以使用添加/删除等方法修改集合。你不能自由地对IEnumerable做同样的事情。

简单的程序:

using System;
using System.Collections;
using System.Collections.Generic;

namespace StackDemo
{
    class Program 
    {
        static void Main(string[] args)
        {
            List<Person> persons = new List<Person>();
            persons.Add(new Person("John",30));
            persons.Add(new Person("Jack", 27));

            ICollection<Person> personCollection = persons;
            IEnumerable<Person> personEnumeration = persons;

            // IEnumeration
            // IEnumration Contains only GetEnumerator method to get Enumerator and make a looping
            foreach (Person p in personEnumeration)
            {                                   
               Console.WriteLine("Name:{0}, Age:{1}", p.Name, p.Age);
            }

            // ICollection
            // ICollection Add/Remove/Contains/Count/CopyTo
            // ICollection is inherited from IEnumerable
            personCollection.Add(new Person("Tim", 10));

            foreach (Person p in personCollection)
            {
                Console.WriteLine("Name:{0}, Age:{1}", p.Name, p.Age);        
            }
            Console.ReadLine();

        }
    }

    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public Person(string name, int age)
        {
            this.Name = name;
            this.Age = age;
        }
    }
}

ICollection和IEnumerable之间有一些基本的区别

IEnumerable -仅包含获取枚举器的GetEnumerator方法，并允许循环 ICollection包含其他方法:添加，删除，包含，计数，CopyTo ICollection继承自IEnumerable 使用ICollection，您可以使用添加/删除等方法修改集合。你不能自由地对IEnumerable做同样的事情。

简单的程序:

using System;
using System.Collections;
using System.Collections.Generic;

namespace StackDemo
{
    class Program 
    {
        static void Main(string[] args)
        {
            List<Person> persons = new List<Person>();
            persons.Add(new Person("John",30));
            persons.Add(new Person("Jack", 27));

            ICollection<Person> personCollection = persons;
            IEnumerable<Person> personEnumeration = persons;

            // IEnumeration
            // IEnumration Contains only GetEnumerator method to get Enumerator and make a looping
            foreach (Person p in personEnumeration)
            {                                   
               Console.WriteLine("Name:{0}, Age:{1}", p.Name, p.Age);
            }

            // ICollection
            // ICollection Add/Remove/Contains/Count/CopyTo
            // ICollection is inherited from IEnumerable
            personCollection.Add(new Person("Tim", 10));

            foreach (Person p in personCollection)
            {
                Console.WriteLine("Name:{0}, Age:{1}", p.Name, p.Age);        
            }
            Console.ReadLine();

        }
    }

    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public Person(string name, int age)
        {
            this.Name = name;
            this.Age = age;
        }
    }
}

导航属性通常被定义为虚拟的，这样它们就可以利用某些实体框架的功能，比如延迟加载。

如果一个导航属性可以保存多个实体(如在多对多或一对多关系中)，那么它的类型必须是一个列表，其中可以添加、删除和更新条目，例如ICollection。

https://www.asp.net/mvc/overview/getting-started/getting-started-with-ef-using-mvc/creating-an-entity-framework-data-model-for-an-asp-net-mvc-application

使用ICollection<T>是因为IEnumerable<T>接口不提供添加项、删除项或以其他方式修改集合的方法。

使用ICollection的基本思想是提供一个接口来快速访问有限数量的数据。事实上，你有一个收藏。数属性。IEnumerable更适合于某些数据链，在这些数据链中，你可以读到某个逻辑点，某个消费者特别指定的条件，或者读到枚举的结尾。

我是这样记得的:

IEnumerable has one method GetEnumerator() which allows one to read through the values in a collection but not write to it. Most of the complexity of using the enumerator is taken care of for us by the for each statement in C#. IEnumerable has one property: Current, which returns the current element. ICollection implements IEnumerable and adds few additional properties the most use of which is Count. The generic version of ICollection implements the Add() and Remove() methods. IList implements both IEnumerable and ICollection, and add the integer indexing access to items (which is not usually required, as ordering is done in database).