c# - 如何从访问托管代码的 native 线程强制使用正确的 AppDomain？

Question

我有一个用 C# 编写的 MMC 管理单元。 MMC 似乎为每个托管管理单元创建了一个单独的 AppDomain。它还为托管系统 dll(如 mscorlib.dll、Microsoft.ManagementConsole.dll 等)提供默认的 AppDomain。

我的管理单元有一个 native C++ dll，它创建可以通过 Interop 调用托管代码的 native 线程。问题是当 native 线程访问我的托管代码时，它会尝试在默认的 AppDomain 中执行此操作，而不是在我的管理单元中。

有没有办法强制 native 线程“切换”到管理单元的 AppDomain？我无法重写 native dll。我唯一能做的就是在这个 dll 将调用的 C++/CLI 中实现一些 C++ 接口(interface)。

下面是最小的、完整的和可验证的示例。要编译它，请在 Visual Studio 中选择 C++/CLR 控制台应用程序项目类型。

#include <Windows.h>
#include <msclr/gcroot.h>

using namespace System;

#pragma unmanaged

class IService
{
public:
    virtual void Operate() = 0;
};

DWORD __stdcall MyNativeThread(LPVOID arg)
{
    IService* service = (IService*)arg;

    service->Operate();

    return 0;
}

void StartNativeThread(IService* service)
{
    CloseHandle(CreateThread(NULL, 0, &MyNativeThread, service, 0, NULL));
}

#pragma managed 

public ref class ServiceManagedImpl
{
public:
    void Operate()
    {
        System::Console::WriteLine("ServiceManagedImpl::Operate: Domain: {0}", System::AppDomain::CurrentDomain->Id);
    }
};

class ServiceImpl : public IService
{
public:
    ServiceImpl(ServiceManagedImpl^ managedImpl)
    {
        m_managedImpl = managedImpl;
    }

    void Operate() override
    {
        m_managedImpl->Operate();
    }

private:
    msclr::gcroot<ServiceManagedImpl^> m_managedImpl;
};

public ref class MyMmcSnapIn : MarshalByRefObject
{
public:
    MyMmcSnapIn()
    {
        System::Console::WriteLine("MyMmcSnapIn.ctor: Domain: {0}", AppDomain::CurrentDomain->Id);

        ServiceImpl testImpl = ServiceImpl(gcnew ServiceManagedImpl());

        StartNativeThread(&testImpl);

        Threading::Thread::Sleep(10000);
    }
};

int main()
{
    Console::WriteLine(L"Main: Domain: {0}", AppDomain::CurrentDomain->Id);

    AppDomain^ mmcSnapInAppDomain = AppDomain::CreateDomain("AppDomainForMyMmcSnapIn");

    // direct instantiation works as expected
    // gcnew MyMmcSnapIn();

    String^ entryAssemblyLocation = Reflection::Assembly::GetEntryAssembly()->Location;
    mmcSnapInAppDomain->CreateInstanceFrom(entryAssemblyLocation, "MyMmcSnapIn");

    return 0;
}

由于错误的 AppDomain 抛出以下异常:

Exception type:   System.ArgumentException
Message:          Cannot pass a GCHandle across AppDomains.
InnerException:   <none>
StackTrace (generated):
    SP       IP       Function
    00000000 00000001 mscorlib_ni!System.Runtime.InteropServices.GCHandle.InternalCheckDomain(IntPtr)+0x2
    01DBFA9C 71FA20C4 mscorlib_ni!System.Runtime.InteropServices.GCHandle.FromIntPtr(IntPtr)+0x34
    01DBFAAC 72721151 mscorlib_ni!System.Runtime.InteropServices.GCHandle.op_Explicit(IntPtr)+0x1d
    01DBFAB4 00361F16 ConsoleApplication15!<Module>.msclr.gcroot<ServiceManagedImpl ^>.->(msclr.gcroot<ServiceManagedImpl ^>*)+0x36
    01DBFAD4 00361EB8 ConsoleApplication15!<Module>.ServiceImpl.Operate(ServiceImpl*)+0x28

Answer 1

这可以按照这里建议的方式完成:

http://www.lenholgate.com/blog/2009/07/error-cannot-pass-a-gchandle-across-appdomains.html

解决方案总结:

The trick is that you need to use a delegate, which knows about the AppDomain that it relates to, and then call through the delegate by converting it to a function pointer. This effectively marshals the unmanaged call into the correct AppDomain before executing the managed c

将解决方案应用于您的代码，它会按预期编译和执行:

#include "stdafx.h"
#include <Windows.h>
#include <msclr/gcroot.h>

using namespace System;
using namespace System::Runtime::InteropServices;

#pragma unmanaged

class IService
{
public:
    virtual void Operate() = 0;
};

DWORD __stdcall MyNativeThread(LPVOID arg)
{
    IService* service = (IService*)arg;

    service->Operate();

    return 0;
}

void StartNativeThread(IService* service)
{
    CloseHandle(CreateThread(NULL, 0, &MyNativeThread, service, 0, NULL));
}

#pragma managed 

typedef void (__stdcall ConnectFnc)();

public ref class ServiceManagedImpl
{
public:
    ServiceManagedImpl()
    {
        m_OperateDelegate = gcnew Delegate(this, &ServiceManagedImpl::Operate);
    }
    ConnectFnc *GetDelegateFunctionPointer()
    {
        return   (ConnectFnc*)(Marshal::GetFunctionPointerForDelegate(m_OperateDelegate).ToPointer());
    }

public:
    void Operate()
    {
        System::Console::WriteLine("ServiceManagedImpl::Operate: Domain: {0}", System::AppDomain::CurrentDomain->Id);
    }
private:
    delegate void Delegate();
    Delegate ^m_OperateDelegate;
};

class ServiceImpl : public IService
{
public:
    ServiceImpl(ServiceManagedImpl^ managedImpl)
    {
        m_managedImpl = new msclr::gcroot<ServiceManagedImpl^>(managedImpl);   
        m_pFunction = (*m_managedImpl)->GetDelegateFunctionPointer();
    }
    ~ServiceImpl()
    {
        delete m_managedImpl;
    }
    void operator()() const
    {
        m_pFunction();
    }

    virtual void Operate() override
    {
        m_pFunction();
    }

private:
    msclr::gcroot<ServiceManagedImpl^> *m_managedImpl;
    ConnectFnc *m_pFunction;
};

public ref class MyMmcSnapIn : MarshalByRefObject
{
public:
    MyMmcSnapIn()
    {
        System::Console::WriteLine("MyMmcSnapIn.ctor: Domain: {0}", AppDomain::CurrentDomain->Id);

        ServiceImpl testImpl = ServiceImpl(gcnew ServiceManagedImpl());

        StartNativeThread(&testImpl);

        Threading::Thread::Sleep(10000);
    }
};

int main()
{
    Console::WriteLine(L"Main: Domain: {0}", AppDomain::CurrentDomain->Id);

    AppDomain^ mmcSnapInAppDomain = AppDomain::CreateDomain("AppDomainForMyMmcSnapIn");

    // direct instantiation works as expected
    // gcnew MyMmcSnapIn();

    String^ entryAssemblyLocation = Reflection::Assembly::GetEntryAssembly()->Location;
    mmcSnapInAppDomain->CreateInstanceFrom(entryAssemblyLocation, "MyMmcSnapIn");

    return 0;
}