前记

JIT\AOT

JIT编译器（Just-in-Time Complier）,AOT编译器（Ahead-of-Time Complier）。

AOT测试

首先编译一段普通代码

using System;
using System.Runtime.InteropServices;
namespace coleak
{
    class winfun
    {
        [DllImport("User32.dll")]
        public static extern int MessageBox(IntPtr h, string m, string c, uint type);
        [DllImport("kernel32.dll", EntryPoint = "Beep")]
        public static extern bool mymethod(uint frequency, uint duration);
    }
        class Program
    {
            static void Main(string[] args)
            {
            winfun winfun = new winfun();
            winfun.MessageBox((IntPtr)0, "yueyy", "coleak",(uint) 0);
            Random random = new Random();
            for (int i = 0; i < 10000; i++)
            {
                winfun.mymethod((uint)random.Next(10000), 100);
            }
            Console.ReadLine();
            }
    }
}

和csc直接编译相比，AOT发布确实可以防止dnspy出源码，但不能解决反汇编，该加壳还是得加壳

优点

不依赖.net框架环境也可以运行
不会被直接反编译而导致代码泄露

缺点

不能Assembly.Load进行动态加载
不支持32位程序

示例如下

using System;
using System.Reflection;
namespace LoadExe
{
    class Program
    {
        static void Main(string[] args)
{
    string base64string = @"";
    byte[] Buffer = Convert.FromBase64String(base64string);
    Assembly assembly = Assembly.Load(Buffer);
    Type type = assembly.GetType("DemoExe.Test");
    MethodInfo method = type.GetMethod("TestMethod");
    Object obj = assembly.CreateInstance(method.Name);
    method.Invoke(obj, null);
}
    }
}

Unhandled Exception: System.PlatformNotSupportedException: Operation is not supported on this platform.
   at Internal.Reflection.Execution.AssemblyBinderImplementation.Bind(ReadOnlySpan`1, ReadOnlySpan`1, AssemblyBindResult&, Exception&) + 0x39
   at System.Reflection.Runtime.Assemblies.RuntimeAssemblyInfo.GetRuntimeAssemblyFromByteArray(ReadOnlySpan`1, ReadOnlySpan`1) + 0x58
   at System.Reflection.Assembly.Load(Byte[], Byte[]) + 0xbe
   at LoadExe.Program.Main(String[] args) + 0x25
   at nativeAOT!<BaseAddress>+0x114a40

但是部分反射api仍然有效

using System;
using System.Reflection;
namespace LoadExe
{
    class Program
    {
        public static void Main()
        {
            Console.Write("Name of type: ");
            string typeName = "LoadExe.Program";
            string methodName = "SayHello";
            Type.GetType(typeName).GetMethod(methodName).Invoke(null, null);
            Console.ReadKey();
        }

        public static void SayHello()
        {
            Console.WriteLine("Hello!");
        }
    }
}

具体规则如下

1.APIs that don’t work and will not work

• APIs that require dynamic code generation: Reflection.Emit, Assembly.Load and friends
• Obvious program introspection APIs: APIs on Type and Assembly not mentioned above, MethodBase, MethodInfo, ConstructorInfo, FieldInfo, PropertyInfo, EventInfo. These APIs will throw at runtime.
• APIs building on top of reflection APIs. Too many to enumerate.

2.Reflection-free mode supports a limited set of reflection APIs that keep their expected semantics.

• typeof(SomeType) will return a System.Type that can be compared with results of other typeof expressions or results of Object.GetType() calls. The patterns commonly used in perf optimizations of generic code (e.g. typeof(T) == typeof(byte)) will work fine, and so will obj.GetType() == typeof(SomeType).
• Following APIs on System.Type work: TypeHandle, UnderlyingSystemType, BaseType, IsByRefLike, IsValueType, GetTypeCode, GetHashCode, GetElementType, GetInterfaces, HasElementType, IsArray, IsByRef, IsPointer, IsPrimitive, IsAssignableFrom, IsAssignableTo, IsInstanceOfType.
• Activator.CreateInstance() will work. The compiler statically analyzes and expands this to efficient code at compile time. No reflection is involved at runtime.
• Assembly.GetExecutingAssembly() will return a System.Reflection.Assembly that can be compared with other runtime Assembly instances. This is mostly to make it possible to use the NativeLibrary.SetDllImportResolver API.

反序列化

JSON格式

using System;
using System.Runtime.Serialization.Json;//添加的引用
namespace ConsoleApp1
{
    public class Book
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public float Price { get; set; }
    }
    public class Program
    {
        static void Main(string[] args)
        {
            //序列化json
            Book book = new Book() { ID = 101, Name = "C#程序设计", Price = 79.5f };
            DataContractJsonSerializer formatter = new DataContractJsonSerializer(typeof(Book));
            using (MemoryStream stream = new MemoryStream())
            {
                formatter.WriteObject(stream, book);
                string result = System.Text.Encoding.UTF8.GetString(stream.ToArray());
                Console.WriteLine(result);
            }
            Console.WriteLine();

            //反序列化json
            string oriStr = "{\"ID\":102,\"Name\":\"C# wpf程序设计\",\"Price\":100}";
            DataContractJsonSerializer formatter1 = new DataContractJsonSerializer(typeof(Book));
            using (MemoryStream stream = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(oriStr)))
            {
                Book outBook = formatter1.ReadObject(stream) as Book;
                Console.WriteLine(outBook.ID);
                Console.WriteLine(outBook.Name);
                Console.WriteLine(outBook.Price);
            }
            Console.ReadLine();
        }
    }
}

Emit

using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;

namespace ConsoleApp1
{
    class Program
    {

        static void Main(string[] args)
        {

            CreateAssembly();
            Console.ReadKey();
        }

        public static void CreateAssembly()
        {
            StringBuilder asmFileNameBldr = new StringBuilder();
            //定义一个程序集的名称
            var asmName = new AssemblyName("MyAssembly");
            //首先就需要定义一个程序集
            AssemblyBuilder defAssembly = AssemblyBuilder.DefineDynamicAssembly(asmName, AssemblyBuilderAccess.RunAndCollect);
            //定义一个构建类DefineDynamicModule
            ModuleBuilder defModuleBuilder = defAssembly.DefineDynamicModule("MyModule");

            //定义一个类
            TypeBuilder typeBuilder = defModuleBuilder.DefineType("MyModule.MyClass", TypeAttributes.Public);

            //定义一个方法
            var defMethodBuilder = typeBuilder.DefineMethod("MyMethod",
                MethodAttributes.Public,
                null,//返回类型
                null//参数类型
                );
            Console.WriteLine($"程序集信息：{typeBuilder.Assembly.FullName}");
            Console.WriteLine($"命名空间：{typeBuilder.Namespace} , 类型：{typeBuilder.Name}");
            //获取IL生成器
            var il = defMethodBuilder.GetILGenerator();
            //定义一个字符串
            il.Emit(OpCodes.Ldstr, "coleak");
            //调用一个函数
            il.Emit(OpCodes.Call, typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }));
            //返回到方法开始（返回）
            il.Emit(OpCodes.Ret);
            //创建类型
            Type dynamicType = typeBuilder.CreateType();
            object ass = Activator.CreateInstance(dynamicType);
            dynamicType.GetMethod("MyMethod").Invoke(ass, null);
        }
    }
}

.NET Framework 中，有 RunAndSave 、Save 等枚举，可用于保存构建的程序集，但是在 .NET Core 中，是没有这些枚举的，也就是说，Emit 构建的程序集只能在内存中，是无法保存成 .dll 文件的