背景介绍

OfType的定义十分简单：IEnumerable.OfType(TResult)，如其定义，其中TRsult为所要过滤的类型。由于非泛型集合一律以Object类型存储对象，因此一个非泛型集合可能存储了各种类型，而OfType()方法可以轻松的对指定的类型进行过滤筛选。

代码如下：

        static void Main(string[] args){            List<Phone> PhoneLists = new List<Phone>(){new Phone { Country = "中国", City = "北京", Name = "小米" },new Phone { Country = "中国",City = "北京",Name = "华为"},new Phone { Country = "中国",City = "北京",Name = "联想"},new Phone { Country = "中国",City = "台北",Name = "魅族"},new Phone { Country = "日本",City = "东京",Name = "索尼"},new Phone { Country = "日本",City = "大阪",Name = "夏普"},new Phone { Country = "日本",City = "东京",Name = "松下"},new Phone { Country = "美国",City = "加州",Name = "苹果"},new Phone { Country = "美国",City = "华盛顿",Name = "三星"},new Phone { Country = "美国",City = "华盛顿",Name = "HTC"}};var Lists = PhoneLists.Select(p => new GetMyPhone().MyPhone(p));var myLists = Lists.OfType<MyPhone>();foreach (var list in myLists){Console.WriteLine($"{list.MyCity} - {list.MyName}");}Console.Read();}public class Phone{public string Country { get; set; }public string City { get; set; }public string Name { get; set; }}public class MyPhone{public string MyCity { get; set; }public string MyName { get; set; }}public class GetMyPhone{public object MyPhone(Phone phone){if (phone.Country.Equals("中国")){MyPhone myphone = new Program.MyPhone(){MyCity = phone.City,MyName = phone.Name};return myphone;}else{return phone;}}}

 GetMyPhone类中的MyPhone方法取出指定条件的Phone，上述代码中是Country为中国，组成MyPhone类型并返回，如果不满足条件则返回原来的类型，这意味着属性Lists中有两种类型的实体类，而OfType可以将其中为MyPhone类型取出。

运行结果如下所示：