使用反射机制是有一些缺点的。其最大的缺点就是编译器无法对对象进行类型检查，此时IDE的智能感知将无能为力。但是他的真正优势又在什么地方呢？它提供了一种手段，将指定具体类推迟到了运行时刻。
使用反射机制调用方法的四步曲：
1 加载程序集
2 获取类的类型
3 创建该类的实例
4 调用该实例的方法
System.Reflection.Assembly类中有两个静态方法Assembly.Load(string assemblyName)和Assembly.LoadFrom(string fileName)来把程序集加载到应用程序序域中。
PS：在。NET中当一个对象被创建时，幕后到底发生了什么？当我们运行某一个应用程序时，.NET CLR会首先创建一个应用程序域来容纳这个应用程序，接着将应该引用的程序集加载到应用程序域中。其中MSCorLib.dll是一个程序集，它包含了很多系统命名空间及其子命名空间中的类：System;System.Text,System.IO等。该程序集合中。然后CLR加载正在运行的应用程序所属的程序集。
DEMO：
(1)namespace ClassLibrarySport
{
public abstract class Sport
{
protected string name;
public abstract string GetName();
public abstract string GetDuration();
}
}
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(2)namespace ClassLibrarySomeSports//该项目添加了对(1)的引用
{
public class Football : ClassLibrarySport.Sport
{
public Football()
{
name = "Football";
}
public override string GetName()
{
return name;
}
public override string GetDuration()
{
return "four 15 minute quarters";
}
}
}
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(3)namespace ConsoleAssemblyTest//该项目添加了对(1)的引用
{
class Program
{
static void Main(string[] args)
{
Assembly assembly = Assembly.LoadFrom(@"E:"ClassLibrarySomeSports"
bin"Debug"ClassLibrarySomeSports.dll");
Type[] types = assembly.GetTypes();
Console.WriteLine("Get Type From ClassLibrarySomeSports.dll:");
for (int i = 0; i < types.Length; i++)
{
Console.WriteLine(types[i].Name);
}
//使用GetConstructor()方法获取对应类型的构造器，从而构造出该类型的对象
Console.WriteLine("Use Method GetConstructor():");
ConstructorInfo ci = types[0].GetConstructor(new Type[0]);
ClassLibrarySport.Sport sport = (ClassLibrarySport.Sport)ci.Invoke(new object[0]);
Console.WriteLine(sport.GetName() + " has " + sport.GetDuration());
//使用Activator.CreateInstance()方法构造出该类型的对象
//使用assembly.CreateInstance()返回为null，？？
Console.WriteLine("Use Method CreateInstance():");
ClassLibrarySport.Sport sport1 = (ClassLibrarySport.Sport)
Activator.CreateInstance(types[0]);
Console.WriteLine(sport1.GetName() + " has " + sport1.GetDuration());
//反射指定类型中的名称为“GetDuration”的方法，通过Invoke()方法执行该方法
object objSport = Activator.CreateInstance(types[0]);
MethodInfo method = types[0].GetMethod("GetDuration");
object o = method.Invoke(objSport, new object[0]);
Console.WriteLine(o as string);
Console.Read();
}
}
}
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Output:
Get Type From ClassLibrarySomeSports.dll:
Football
Use Method GetConstructor():
Football has four 15 minute quarters
Use Method CreateInstance():
Football has four 15 minute quarters
four 15 minute quarters