////////////C#基础 Type IsAssignableFrom 类是否实现了指定的接口
using System;
namespace ConsoleApp
{
public interface ISayHello
{
void SayHello();
}
class CapablePerson : ISayHello
{
public void SayHello()
{
throw new NotImplementedException();
}
}
class UnachievablePerson
{
}
class Program
{
static void Main(string[] args)
{
Type tpISayHello = typeof(ISayHello);
Type tpCapablePersonClass = typeof(CapablePerson);
Type tpUnachievablePersonClass = typeof(UnachievablePerson);
if (tpISayHello.IsAssignableFrom(tpCapablePersonClass))
{
Console.WriteLine(tpCapablePersonClass.Name + "实现了接口" + tpISayHello.Name);
}
else
{
Console.WriteLine(tpCapablePersonClass.Name + "没有实现接口" + tpISayHello.Name);
}
if (tpISayHello.IsAssignableFrom(tpUnachievablePersonClass))
{
Console.WriteLine(tpUnachievablePersonClass.Name + "实现了接口" + tpISayHello.Name);
}
else
{
Console.WriteLine(tpUnachievablePersonClass.Name + "没有实现了接口" + tpISayHello.Name);
}
Console.ReadKey();
}
}
}
////Result:
CapablePerson实现了接口ISayHelloUnachievablePerson没有实现了接口ISayHello////////////////////////////////////////////////////////////////////
C# IsAssignableFrom与IsSubClassOf 判断匿名类是否继承父类
public class Dog : Animal
{
public string name { get; set; }
}
public class Animal
{
public string id { get; set; }
}
public class Main
{
public void Main()
{
Dog aa = new Dog { name = "狗", id = "动物" };
CheckClass(aa);
}
public void CheckClass<T>(T entity)
{
bool re1 = typeof(Animal).IsAssignableFrom(typeof(T));
//返回true的条件是Dog类直接或间接的实现了Animal类;
bool re2 = typeof(T).IsSubclassOf(typeof(Animal));
//返回true的条件是Dog类是Animal的子类
var id = (entity as Animal).id;
}
}
///////////////////////////////////////////////////////////
首先说下 IsGenericType
用3个实例说明:
typeof(DateTime).IsGenericType : false
typeof(List<int>).IsGenericType: true
typeof(Dictionary<,>).IsGenericType:true
类型如果是泛型则为 true
但是要注意以下情况:
T[], List[] 等等数组时, IsGenericType为False
typeof(T[]).GetElementType().IsGenericType才是True
接着说 IsGenericTypeDefinition
用2个实例说明:
typeof(List<int>).IsGenericTypeDefintion : false
typeof(List<>).IsGenericTypeDefinition :true
IsGenericTypeDefinition ： 获取一个值，该值指示当前 Type 是否表示可以用来构造其他泛型类型的泛型类型定义。
也就是说表明 这个 type 是否可以用于构建泛型定义
比如 List<> 可以通过反射构建出 List,List
例子:
var typeList = typeof(List<>);
Type typeDataList = typeList.MakeGenericType( typeof(DateTime)); //通过List<>构建出List<DateTime>
最后说下 IsGenericParameter
这个Property用于表明当前类型是一个T类型
例如:
typeof(List<>).GetGenericArguments()
返回: new Type[]{ typeof(T) }
此时:
typeof(List<>).GetGenericArguments()
返回: new Type[]{ typeof(T) }
此时:
typeof(T).IsGenericParameter == True
typeof(T).GenericParameterPosition == 0
对比:
typeof(List<DateTime>).GetGenericArguments()
返回: new Type[]{ typeof(DateTime) }
此时:
typeof(DateTime).IsGenericParameter == False
typeof(DateTime).GenericParameterPosition : throw exception
///////////////////////////////////////////////////////////
////////////////////////////////////////////Dot Net 高性能代码/////////////////////////////////////////////////////////////////
C# AggressiveInlining: MethodImpl Attribute
Benchmark and test the AggressiveInlining option. Use MethodImplOptions.AggressiveInlining.
AggressiveInlining. The JIT compiler logically determines which methods to inline. But sometimes we know better than it does. With AggressiveInlining, we give the compiler a hint. We tell it that the method should be inlined.
Attribute
Optimization
Example. This example benchmarks a method with no attribute, and with AggressiveInlining. The method body contains several lines of useless code. This makes the method large in bytes, so the JIT compiler may decide not to inline it.
Benchmark
And: We apply the MethodImplOptions.AggressiveInlining option to Method2. This is an enum.
Result: We see that with no options, the method calls required seven nanoseconds each.
But: With inlining specified (with AggressiveInlining), the calls required less than one nanosecond each.
C# program that uses AggressiveInlining
using System;
using System.Diagnostics;
using System.Runtime.CompilerServices;
class Program {
const int _max = 10000000;
static void Main() {
// ... Compile the methods.
Method1();
Method2();
int sum = 0;
var s1 = Stopwatch.StartNew();
for (int i = 0; i < _max; i++) {
sum += Method1(); }
s1.Stop();
var s2 = Stopwatch.StartNew();
for (int i = 0; i < _max; i++) {
sum += Method2(); }
s2.Stop(); Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns")); Console.Read(); }
static int Method1() {
// ... No inlining suggestion.
return "one".Length + "two".Length + "three".Length + "four".Length + "five".Length + "six".Length + "seven".Length + "eight".Length + "nine".Length + "ten".Length;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static int Method2() {
// ... Aggressive inlining.
return "one".Length + "two".Length + "three".Length + "four".Length + "five".Length + "six".Length + "seven".Length + "eight".Length + "nine".Length + "ten".Length;
}
}
Output
7.34 ns No options
0.32 ns MethodImplOptions.AggressiveInlining
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
