.Net core 的热插拔机制的深入探索及卸载问题求救指南

{
 "runtimeTarget": {
 "name": ".NETCoreApp,Version=v3.1",
 "signature": ""
 },
 "compilationOptions": {},
 "targets": {
 ".NETCoreApp,Version=v3.1": {
 "PluginSample/1.0.0": {
 "dependencies": {
 "Microsoft.Extensions.Hosting.Abstractions": "5.0.0-rc.2.20475.5"
 },
 "runtime": {
 "PluginSample.dll": {}
 }
 },
 "Microsoft.Extensions.Configuration.Abstractions/5.0.0-rc.2.20475.5": {
 "dependencies": {
 "Microsoft.Extensions.Primitives": "5.0.0-rc.2.20475.5"
 },
 "runtime": {
 "lib/netstandard2.0/Microsoft.Extensions.Configuration.Abstractions.dll": {
 "assemblyVersion": "5.0.0.0",
 "fileVersion": "5.0.20.47505"
 }
 }
 ...

using (var dependencyFileStream = File.OpenRead("Sample.deps.json"))
{
 using (DependencyContextJsonReader dependencyContextJsonReader = new DependencyContextJsonReader())
 {
 //得到对应的实体文件
 var dependencyContext = 
 dependencyContextJsonReader.Read(dependencyFileStream);
 //定义的运行环境,没有,则为全平台运行.
 string currentRuntimeIdentifier= dependencyContext.Target.Runtime;
 //运行时所需要的dll文件
 var assemblyNames= dependencyContext.RuntimeLibraries;
 }
}

{
 "runtimes": {
 "win-arm64": {
 "#import": [
 "win"
 ]
 },
 "win-arm64-aot": {
 "#import": [
 "win-aot",
 "win-arm64"
 ]
 },
 "win-x64": {
 "#import": [
 "win"
 ]
 },
 "win-x64-aot": {
 "#import": [
 "win-aot",
 "win-x64"
 ]
 },
}

win7-x64 win7-x86
 | \ / |
 | win7 |
 | | |
win-x64 | win-x86
 \ | /
 win
 |
 any

public class PluginLoadContext : AssemblyLoadContext
{
 private AssemblyDependencyResolver _resolver;
 public PluginLoadContext(string pluginFolder, params string[] commonAssemblyFolders) : base(isCollectible: true)
 {
 this.ResolvingUnmanagedDll += PluginLoadContext_ResolvingUnmanagedDll;
 this.Resolving += PluginLoadContext_Resolving;
 //第1步,解析des.json文件,并调用Load和LoadUnmanagedDll函数
 _resolver = new AssemblyDependencyResolver(pluginFolder);
 //第6步,通过第4,5步,解析仍失败的dll会自动尝试调用主程序中的程序集,
 //如果失败,则直接抛出程序集无法加载的错误
 }
 private Assembly PluginLoadContext_Resolving(AssemblyLoadContext assemblyLoadContext, AssemblyName assemblyName)
 {
 //第4步,Load函数加载程序集失败后,执行的事件
 }
 private IntPtr PluginLoadContext_ResolvingUnmanagedDll(Assembly assembly, string unmanagedDllName)
 {
 //第5步,LoadUnmanagedDll加载native dll失败后执行的事件
 }
 protected override Assembly Load(AssemblyName assemblyName)
 {
 //第2步,先执行程序集的加载函数
 }
 protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
 {
 //第3步,先执行的native dll加载逻辑
 }
}

class PluginLoadContext : AssemblyLoadContext
{
 private AssemblyDependencyResolver _resolver;

 public PluginLoadContext(string pluginPath)
 {
 _resolver = new AssemblyDependencyResolver(pluginPath);
 }

 protected override Assembly Load(AssemblyName assemblyName)
 {
 string assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
 if (assemblyPath != null)
 {
 //加载程序集
 return LoadFromAssemblyPath(assemblyPath);
 }
 //返回null,则直接加载主项目程序集
 return null;
 }

 protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
 {
 string libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
 if (libraryPath != null)
 {
 //加载native dll文件
 return LoadUnmanagedDllFromPath(libraryPath);
 }
 //返回IntPtr.Zero,即null指针.将会加载主项中runtimes文件夹下的dll
 return IntPtr.Zero;
 }
}

namespace PluginSample
{
 public class SimpleService
 {
 public void Run(string name)
 {
 Console.WriteLine($"Hello World!");
 }
 }
}

namespace Test
{
 public class PluginLoader
 {
 pubilc AssemblyLoadContext assemblyLoadContext;
 public Assembly assembly;
 public Type type;
 public MethodInfo method;
 public void Load()
 {
 assemblyLoadContext = new PluginLoadContext("插件文件夹");
 assembly = alc.Load(new AssemblyName("PluginSample"));
 type = assembly.GetType("PluginSample.SimpleService");
 method=type.GetMethod()
 }
 }
}

public void Load(out WeakReference weakReference)
 {
 var assemblyLoadContext = new PluginLoadContext("插件文件夹");
 weakReference = new WeakReference(pluginLoadContext, true);
 assemblyLoadContext.UnLoad();
 }
 public void Check()
 {
 WeakReference weakReference=null;
 Load(out weakReference);
 //一般第二次,IsAlive就会变为False,即AssemblyLoadContext卸载失败.
 for (int i = 0; weakReference.IsAlive && (i < 10); i++)
 {
 GC.Collect();
 GC.WaitForPendingFinalizers();
 }
 }

public class SimpleService
{
 //同步执行,插件卸载成功
 public void Run(string name)
 {
 Console.WriteLine($"Hello {name}!");
 }
 //异步执行,卸载成功
 public Task RunAsync(string name)
 {
 Console.WriteLine($"Hello {name}!");
 return Task.CompletedTask;
 }
 //异步执行,卸载成功
 public Task RunTask(string name)
 {
 return Task.Run(() => {
 Console.WriteLine($"Hello {name}!");
 });
 }
 //异步执行,卸载成功
 public Task RunWaitTask(string name)
 {
 return Task.Run( async ()=> {
 while (true)
 {
 if (CancellationTokenSource.IsCancellationRequested)
 {
  break;
 }
 await Task.Delay(1000);
 Console.WriteLine($"Hello {name}!");
 }
 });
 }
 //异步执行,卸载成功
 public Task RunWaitTaskForCancel(string name, CancellationToken cancellation)
 {
 return Task.Run(async () => {
 while (true)
 {
 if (cancellation.IsCancellationRequested)
 {
  break;
 }
 await Task.Delay(1000);
 Console.WriteLine($"Hello {name}!");
 }
 });
 }
 //异步执行,卸载失败
 public async Task RunWait(string name)
 {
 while (true)
 {
 if (CancellationTokenSource.IsCancellationRequested)
 {
 break;
 }
 await Task.Delay(1000);
 Console.WriteLine($"Hello {name}!");
 }

 }
 //异步执行,卸载失败
 public Task RunWaitNewTask(string name)
 {
 return Task.Factory.StartNew(async ()=> {
 while (true)
 {
 if (CancellationTokenSource.IsCancellationRequested)
 {
  break;
 }
 await Task.Delay(1000);
 Console.WriteLine($"Hello {name}!");
 }
 },TaskCreationOptions.DenyChildAttach);
 }
}