DLL：程序集，包含IL 和Metadada
IL：面向对象中间语言（不太好阅读）
Metadata描述了dll、exe中的各种类、属性、方法、参数等信息。
反射 Reflection： .NET Framework提供的帮助类库，可以读取Metadata。
C# 高级语言经过编译器编译生成DLL/EXE，DLL/EXE中包含了Metadata和IL，CLR先读取DLL/EXE中的Metadata，然后JIT进行二次编译，编译成机器码。
Assembly assembly = Assembly.Load("XF.DB.SqlServer");//动态加载，需要提供完整的DLL名，不需要后缀,从exe所在的路径进行查找
Assembly assembly2 = Assembly.LoadFile(@"C:\HXF_CODE\02.Code\05.NET Code\XF.High.NET.Study\XF.DB.SqlServer\bin\Debug\XF.DB.Sqlserver.dll");
Assembly assembly3 = Assembly.LoadFrom("XF.DB.SqlServer.dll");
Assembly assembly4 = Assembly.LoadFrom(@"C:\HXF_CODE\02.Code\05.NET Code\XF.High.NET.Study\XF.DB.SqlServer\bin\Debug\XF.DB.Sqlserver.dll");
Type type = assembly.GetType("XF.DB.SqlServer.SqlServerHelper");//获取类型，需要提供完整的类型名称
object sqlServerHelper = Activator.CreateInstance(type);
IDBHelper dbHelper = sqlServerHelper as IDBHelper;
dbHelper.Query();
2.2.创建多构造函数对象：
object ctor1 = Activator.CreateInstance(type);
object ctor2 = Activator.CreateInstance(type, new object[] { 123 });
object ctor3 = Activator.CreateInstance(type, new object[] { "Olive" });
程序可配置，通过配置文件自动切换
实现类必须是事先已有的，且存在运行目录下
没有写死类型，通过配置文件执行，反射创建
可扩展：不修改原有代码，只是增加新的实现，修改配置即可支持新功能
反射动态加载、创建对象，与配置文件结合。
private static string typeStr = ConfigurationManager.AppSettings["IDBHelperConfig"];
//反射动态加载、创建对象结合配置文件
{
string[] typeArr = typeStr.Split(‘,‘);
Assembly assembly1 = Assembly.Load(typeArr[1]);
Type type = assembly1.GetType(typeArr[0]);
foreach (var ctor in type.GetConstructors())
{
Console.WriteLine(ctor.Name);
foreach (var parameter in ctor.GetParameters())
{
Console.WriteLine(parameter.ParameterType);
}
}
object ctor1 = Activator.CreateInstance(type);
object ctor2 = Activator.CreateInstance(type, new object[] { 123 });
object ctor3 = Activator.CreateInstance(type, new object[] { "Olive" });
}
反射破坏单例（调用私有的构造函数）
//反射破坏单例（调用私有的构造函数）
Assembly assembly5 = Assembly.Load("XF.DB.SqlServer");
Type type1 = assembly.GetType("XF.DB.SqlServer.Singleton");
Singleton singleton4 = (Singleton)Activator.CreateInstance(type1, true);
Singleton singleton5 = (Singleton)Activator.CreateInstance(type1, true);
Singleton singleton6 = (Singleton)Activator.CreateInstance(type1, true);
Console.WriteLine($"{object.ReferenceEquals(singleton4, singleton6)}");
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly.GetType("XF.DB.SqlServer.GenericClass`3");//`3为类型占位符，有几个类型就是几，这里有3个类型
Type typeMake = type2.MakeGenericType(new Type[] { typeof(string), typeof(int), typeof(DateTime) });//确定泛型的类型
object genericInstance = Activator.CreateInstance(typeMake);//在创建实例的时候，一定要明确具体的类型
GenericClass<string,int,DateTime> gc = genericInstance as GenericClass<string, int, DateTime>;
gc.Show("Olive", 116, DateTime.Now);
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly6.GetType("XF.DB.SqlServer.ReflectionTest");
object test = Activator.CreateInstance(type2);
MethodInfo method = type2.GetMethod("Show");//调用无参函数
method.Invoke(test, null);
MethodInfo method1 = type2.GetMethod("Show1");//调用有参函数
method1.Invoke(test,new object[] { "Olive" });
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly6.GetType("XF.DB.SqlServer.ReflectionTest");
object test = Activator.CreateInstance(type2);
MethodInfo method6 = type2.GetMethod("Show4");//调用静态函数，实例可要
method6.Invoke(test, new object[] { "Olive" });
MethodInfo method7 = type2.GetMethod("Show4");//调用静态函数，实例为空
method7.Invoke(null, new object[] { "Olive" });
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly6.GetType("XF.DB.SqlServer.ReflectionTest");
object test = Activator.CreateInstance(type2);
MethodInfo method2 = type2.GetMethod("Show2", new Type[] { });//调用重载函数，无参
method2.Invoke(test, null);
MethodInfo method3 = type2.GetMethod("Show2", new Type[] {typeof(int) });//调用重载函数
method3.Invoke(test, new object[] { 116 });
MethodInfo method4 = type2.GetMethod("Show2", new Type[] {typeof(string),typeof(int) });//调用重载函数
method4.Invoke(test, new object[] { "Olive",116 });
MethodInfo method5 = type2.GetMethod("Show2", new Type[] { typeof(int) ,typeof(string)});//调用重载函数
method5.Invoke(test, new object[] { 116,"Olive" });
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly6.GetType("XF.DB.SqlServer.ReflectionTest");
object test = Activator.CreateInstance(type2);
MethodInfo method8 = type2.GetMethod("Show3",BindingFlags.Instance|BindingFlags.NonPublic);//调用私有函数
method8.Invoke(test, new object[] { "Olive" });
Assembly assembly6 = Assembly.Load("XF.DB.SqlServer");
Type type2 = assembly6.GetType("XF.DB.SqlServer.GenericMethod");
object test = Activator.CreateInstance(type2);
MethodInfo method = type2.GetMethod("Show");//调用无参函数
var methodNew = method.MakeGenericMethod(new Type[] { typeof(string), typeof(int), typeof(DateTime) });
methodNew.Invoke(test,new object[] { "Olive", 116, DateTime.Now });
Type type2 = assembly6.GetType("XF.DB.SqlServer.GenericDouble`1");
Type type3 = type2.MakeGenericType(new Type[] { typeof(int) });
object test = Activator.CreateInstance(type3);
MethodInfo method = type3.GetMethod("Show");
var methodNew = method.MakeGenericMethod(new Type[] { typeof(string), typeof(DateTime) });
methodNew.Invoke(test, new object[] { 116, "Olive", DateTime.Now });
Assembly assembly6 = Assembly.Load("XF.Model");
Type type = assembly6.GetType("XF.Model.People");
object people = Activator.CreateInstance(type);
foreach(var field in type.GetFields())
{
Console.WriteLine($"{type.Name}.{field.Name}={field.GetValue(people)}");
if (field.Name.Equals("Description"))
field.SetValue(people, "Good boy");
}
Assembly assembly6 = Assembly.Load("XF.Model");
Type type = assembly6.GetType("XF.Model.People");
object people = Activator.CreateInstance(type);
foreach(var prop in type.GetProperties())
{
Console.WriteLine($"{type.Name}.{prop.Name}={prop.GetValue(people)}");
if (prop.Name.Equals("Id"))
prop.SetValue(people, 116);
}
好处：动态
局限：使用麻烦
避开编译器检查
性能问题：正常情况下基本上不存在性能问题
原文：https://www.cnblogs.com/Olive116/p/12340323.html