/// <summary>
/// 测试泛型约束
/// </summary>
static void TestGenericConstraint()
{
GenericConstraint <int, Course, Teacher> generic = new GenericConstraint <int, Course, Teacher>();
//给对象属性赋值
generic.ProductList = new List <Course>
{
new Course {
CourseName = "英语", Id = 1000
},
new Course {
CourseName = "数学", Id = 1000
},
new Course {
CourseName = "物理", Id = 1000
}
};
generic.Publish = new Teacher()
{
TeacherName = "常老师", CourseCount = 3
};
var course = generic.ByCourse(0);
Console.WriteLine($"课程老师：{generic.Publish.TeacherName},课程Id{course.Id},课程名称{course.CourseName}");
}
/// <summary>
/// 1 引入泛型：延迟声明
/// 2 如何声明和使用泛型
/// 3 泛型的好处和原理
/// 4 泛型类、泛型方法、泛型接口、泛型委托
/// 5 泛型约束
/// 6 协变、逆变
/// 7 泛型缓存
/// </summary>
static void Main(string[] args)
{
try
{
int iValue = 123;
string sValue = "456";
DateTime dtValue = DateTime.Now;
object oValue = "789";
Console.WriteLine("*************** Common *****************");
CommonMethod.ShowInt(iValue);
CommonMethod.ShowString(sValue);
CommonMethod.ShowDateTime(dtValue);
Console.WriteLine("*************** Object *****************");
CommonMethod.ShowObject(iValue);
CommonMethod.ShowObject(sValue);
CommonMethod.ShowObject(dtValue);
CommonMethod.ShowObject(oValue);
Console.WriteLine("*************** Generic ****************");
CommonMethod.Show <int>(iValue); // 调用泛型，需要指定类型参数
CommonMethod.Show(iValue); // 如果可以从参数类型推断，可以省略类型参数
CommonMethod.Show <string>(sValue);
CommonMethod.Show <DateTime>(dtValue);
CommonMethod.Show <object>(oValue);
Console.WriteLine("************** 泛型原理 *****************");
// 泛型是 .net framework 2.0 推出的，是框架升级的产物
// 支持基础：
// 1. 编译器支持类型参数，用占位符表示的
// 2. CLR升级 CLR 2.0 （.net framework 2.0 - 4.0），运行时类型确定后再替换占位符
Console.WriteLine(typeof(List <>));
Console.WriteLine(typeof(Dictionary <,>));
Console.WriteLine("************** Monitor *****************");
// 泛型方法的性能与普通方法大致一致，是最好的
// 可以一个方法满足多个不同的类型
// object 装箱拆箱过程消耗大量性能
Monitor.Show();
Console.WriteLine("*********** GenericCache ***************");
GenericCacheTest.Show();
Console.WriteLine("******** GenericConstraint *************");
People people = new People()
{
Id = 001, Name = "Jone"
};
Chinese chinese = new Chinese()
{
Id = 002, Name = "Mike"
};
Hubei hubei = new Hubei()
{
Id = 003, Name = "Mirry"
};
Japanese japanese = new Japanese()
{
Id = 004, Name = "Jakey"
};
GenericConstraint.ShowObject(people);
GenericConstraint.ShowObject(chinese);
GenericConstraint.ShowObject(hubei);
// error: 编译通过，运行时报错
// 没有约束，任何类型都能传递进来，所以不安全
// GenericConstraint.ShowObject(japanese);
GenericConstraint.Show(people);
GenericConstraint.Show(chinese);
GenericConstraint.Show(hubei);
// error: 编译不通过
// GenericConstraint.Show(Japanese);
Console.WriteLine("******** 协变、逆变 *************");
CCTest.Show();
}
catch (Exception)
{
throw;
}
}
