native C++ 动态调用.NET DLL

关于这个问题找了好多地方，都只有第二种解决办法，可是我要返回一个字符串，没办法，继续找，最后还是在http://blogs.msdn.com/b/msdnforum/archive/2010/07/09/use-clr4-hosting-api-to-invoke-net-assembly-from-native-c.aspx找到了解决的办法，这里记下来备忘。

转发下范例包：http://files.cnblogs.com/files/maintell/Cpp_app_hosts_CLR_4_and_invokes_.NET_assembly_%28CppHostCLR%29.zip

第一种可以返回一个任意变量或者对象，第二种简单点，只能返回整型，具体看代码：

//
//   FUNCTION: RuntimeHostV4Demo1(PCWSTR, PCWSTR)
//
//   PURPOSE: The function demonstrates using .NET Framework 4.0 Hosting 
//   Interfaces to host a .NET runtime, and use the ICorRuntimeHost interface
//   that was provided in .NET v1.x to load a .NET assembly and invoke its 
//   type. 
//   
//   If the .NET runtime specified by the pszVersion parameter cannot be 
//   loaded into the current process, the function prints ".NET runtime <the 
//   runtime version> cannot be loaded", and return.
//   
//   If the .NET runtime is successfully loaded, the function loads the 
//   assembly identified by the pszAssemblyName parameter. Next, the function 
//   instantiates the class (pszClassName) in the assembly, calls its 
//   ToString() member method, and print the result. Last, the demo invokes 
//   the public static function 'int GetStringLength(string str)' of the class 
//   and print the result too.
//
//   PARAMETERS:
//   * pszVersion - The desired DOTNETFX version, in the format “vX.X.XXXXX”. 
//     The parameter must not be NULL. It’s important to note that this 
//     parameter should match exactly the directory names for each version of
//     the framework, under C:WindowsMicrosoft.NETFramework[64]. The 
//     current possible values are "v1.0.3705", "v1.1.4322", "v2.0.50727" and 
//     "v4.0.30319". Also, note that the “v” prefix is mandatory.
//   * pszAssemblyName - The display name of the assembly to be loaded, such 
//     as "CSClassLibrary". The ".DLL" file extension is not appended.
//   * pszClassName - The name of the Type that defines the method to invoke.
//
//   RETURN VALUE: HRESULT of the demo.
//
HRESULT RuntimeHostV4Demo1(PCWSTR pszVersion, PCWSTR pszAssemblyName, 
    PCWSTR pszClassName)
{
    HRESULT hr;

    ICLRMetaHost *pMetaHost = NULL;
    ICLRRuntimeInfo *pRuntimeInfo = NULL;

    // ICorRuntimeHost and ICLRRuntimeHost are the two CLR hosting interfaces
    // supported by CLR 4.0. Here we demo the ICorRuntimeHost interface that 
    // was provided in .NET v1.x, and is compatible with all .NET Frameworks. 
    ICorRuntimeHost *pCorRuntimeHost = NULL;

    IUnknownPtr spAppDomainThunk = NULL;
    _AppDomainPtr spDefaultAppDomain = NULL;

    // The .NET assembly to load.
    bstr_t bstrAssemblyName(pszAssemblyName);
    _AssemblyPtr spAssembly = NULL;

    // The .NET class to instantiate.
    bstr_t bstrClassName(pszClassName);
    _TypePtr spType = NULL;
    variant_t vtObject;
    variant_t vtEmpty;

    // The static method in the .NET class to invoke.
    bstr_t bstrStaticMethodName(L"GetStringLength");
    SAFEARRAY *psaStaticMethodArgs = NULL;
    variant_t vtStringArg(L"HelloWorld");
    variant_t vtLengthRet;

    // The instance method in the .NET class to invoke.
    bstr_t bstrMethodName(L"ToString");
    SAFEARRAY *psaMethodArgs = NULL;
    variant_t vtStringRet;

    // 
    // Load and start the .NET runtime.
    // 

    wprintf(L"Load and start the .NET runtime %s 
", pszVersion);

    hr = CLRCreateInstance(CLSID_CLRMetaHost, IID_PPV_ARGS(&pMetaHost));
    if (FAILED(hr))
    {
        wprintf(L"CLRCreateInstance failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Get the ICLRRuntimeInfo corresponding to a particular CLR version. It 
    // supersedes CorBindToRuntimeEx with STARTUP_LOADER_SAFEMODE.
    hr = pMetaHost->GetRuntime(pszVersion, IID_PPV_ARGS(&pRuntimeInfo));
    if (FAILED(hr))
    {
        wprintf(L"ICLRMetaHost::GetRuntime failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Check if the specified runtime can be loaded into the process. This 
    // method will take into account other runtimes that may already be 
    // loaded into the process and set pbLoadable to TRUE if this runtime can 
    // be loaded in an in-process side-by-side fashion. 
    BOOL fLoadable;
    hr = pRuntimeInfo->IsLoadable(&fLoadable);
    if (FAILED(hr))
    {
        wprintf(L"ICLRRuntimeInfo::IsLoadable failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    if (!fLoadable)
    {
        wprintf(L".NET runtime %s cannot be loaded
", pszVersion);
        goto Cleanup;
    }

    // Load the CLR into the current process and return a runtime interface 
    // pointer. ICorRuntimeHost and ICLRRuntimeHost are the two CLR hosting  
    // interfaces supported by CLR 4.0. Here we demo the ICorRuntimeHost 
    // interface that was provided in .NET v1.x, and is compatible with all 
    // .NET Frameworks. 
    hr = pRuntimeInfo->GetInterface(CLSID_CorRuntimeHost, 
        IID_PPV_ARGS(&pCorRuntimeHost));
    if (FAILED(hr))
    {
        wprintf(L"ICLRRuntimeInfo::GetInterface failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Start the CLR.
    hr = pCorRuntimeHost->Start();
    if (FAILED(hr))
    {
        wprintf(L"CLR failed to start w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // 
    // Load the NET assembly. Call the static method GetStringLength of the 
    // class CSSimpleObject. Instantiate the class CSSimpleObject and call 
    // its instance method ToString.
    // 

    // The following C++ code does the same thing as this C# code:
    // 
    //   Assembly assembly = AppDomain.CurrentDomain.Load(pszAssemblyName);
    //   object length = type.InvokeMember("GetStringLength", 
    //       BindingFlags.InvokeMethod | BindingFlags.Static | 
    //       BindingFlags.Public, null, null, new object[] { "HelloWorld" });
    //   object obj = assembly.CreateInstance("CSClassLibrary.CSSimpleObject");
    //   object str = type.InvokeMember("ToString", 
    //       BindingFlags.InvokeMethod | BindingFlags.Instance | 
    //       BindingFlags.Public, null, obj, new object[] { });

    // Get a pointer to the default AppDomain in the CLR.
    hr = pCorRuntimeHost->GetDefaultDomain(&spAppDomainThunk);
    if (FAILED(hr))
    {
        wprintf(L"ICorRuntimeHost::GetDefaultDomain failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    hr = spAppDomainThunk->QueryInterface(IID_PPV_ARGS(&spDefaultAppDomain));
    if (FAILED(hr))
    {
        wprintf(L"Failed to get default AppDomain w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Load the .NET assembly.
    wprintf(L"Load the assembly %s
", pszAssemblyName);
    hr = spDefaultAppDomain->Load_2(bstrAssemblyName, &spAssembly);
    if (FAILED(hr))
    {
        wprintf(L"Failed to load the assembly w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Get the Type of CSSimpleObject.
    hr = spAssembly->GetType_2(bstrClassName, &spType);
    if (FAILED(hr))
    {
        wprintf(L"Failed to get the Type interface w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Call the static method of the class: 
    //   public static int GetStringLength(string str);

    // Create a safe array to contain the arguments of the method. The safe 
    // array must be created with vt = VT_VARIANT because .NET reflection 
    // expects an array of Object - VT_VARIANT. There is only one argument, 
    // so cElements = 1.
    psaStaticMethodArgs = SafeArrayCreateVector(VT_VARIANT, 0, 1);
    LONG index = 0;
    hr = SafeArrayPutElement(psaStaticMethodArgs, &index, &vtStringArg);
    if (FAILED(hr))
    {
        wprintf(L"SafeArrayPutElement failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Invoke the "GetStringLength" method from the Type interface.
    hr = spType->InvokeMember_3(bstrStaticMethodName, static_cast<BindingFlags>(
        BindingFlags_InvokeMethod | BindingFlags_Static | BindingFlags_Public), 
        NULL, vtEmpty, psaStaticMethodArgs, &vtLengthRet);
    if (FAILED(hr))
    {
        wprintf(L"Failed to invoke GetStringLength w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Print the call result of the static method.
    wprintf(L"Call %s.%s("%s") => %s
", 
        static_cast<PCWSTR>(bstrClassName), 
        static_cast<PCWSTR>(bstrStaticMethodName), 
        static_cast<PCWSTR>(vtStringArg.bstrVal), 
        vtLengthRet.lVal);

    // Instantiate the class.
    hr = spAssembly->CreateInstance(bstrClassName, &vtObject);
    if (FAILED(hr))
    {
        wprintf(L"Assembly::CreateInstance failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Call the instance method of the class.
    //   public string ToString();

    // Create a safe array to contain the arguments of the method.
    psaMethodArgs = SafeArrayCreateVector(VT_VARIANT, 0, 0);

    // Invoke the "ToString" method from the Type interface.
    hr = spType->InvokeMember_3(bstrMethodName, static_cast<BindingFlags>(
        BindingFlags_InvokeMethod | BindingFlags_Instance | BindingFlags_Public),
        NULL, vtObject, psaMethodArgs, &vtStringRet);
    if (FAILED(hr))
    {
        wprintf(L"Failed to invoke ToString w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Print the call result of the method.
    wprintf(L"Call %s.%s() => %s
", 
        static_cast<PCWSTR>(bstrClassName), 
        static_cast<PCWSTR>(bstrMethodName), 
        static_cast<PCWSTR>(vtStringRet.bstrVal));

Cleanup:

    if (pMetaHost)
    {
        pMetaHost->Release();
        pMetaHost = NULL;
    }
    if (pRuntimeInfo)
    {
        pRuntimeInfo->Release();
        pRuntimeInfo = NULL;
    }
    if (pCorRuntimeHost)
    {
        // Please note that after a call to Stop, the CLR cannot be 
        // reinitialized into the same process. This step is usually not 
        // necessary. You can leave the .NET runtime loaded in your process.
        //wprintf(L"Stop the .NET runtime
");
        //pCorRuntimeHost->Stop();

        pCorRuntimeHost->Release();
        pCorRuntimeHost = NULL;
    }

    if (psaStaticMethodArgs)
    {
        SafeArrayDestroy(psaStaticMethodArgs);
        psaStaticMethodArgs = NULL;
    }
    if (psaMethodArgs)
    {
        SafeArrayDestroy(psaMethodArgs);
        psaMethodArgs = NULL;
    }

    return hr;
}

第二种比较简单：

//
//   FUNCTION: RuntimeHostV4Demo2(PCWSTR, PCWSTR)
//
//   PURPOSE: The function demonstrates using .NET Framework 4.0 Hosting 
//   Interfaces to host a .NET runtime, and use the ICLRRuntimeHost interface
//   that was provided in .NET v2.0 to load a .NET assembly and invoke its 
//   type. Because ICLRRuntimeHost is not compatible with .NET runtime v1.x, 
//   the requested runtime must not be v1.x.
//   
//   If the .NET runtime specified by the pszVersion parameter cannot be 
//   loaded into the current process, the function prints ".NET runtime <the 
//   runtime version> cannot be loaded", and return.
//   
//   If the .NET runtime is successfully loaded, the function loads the 
//   assembly identified by the pszAssemblyName parameter. Next, the function 
//   invokes the public static function 'int GetStringLength(string str)' of 
//   the class and print the result.
//
//   PARAMETERS:
//   * pszVersion - The desired DOTNETFX version, in the format “vX.X.XXXXX”. 
//     The parameter must not be NULL. It’s important to note that this 
//     parameter should match exactly the directory names for each version of
//     the framework, under C:WindowsMicrosoft.NETFramework[64]. Because 
//     the ICLRRuntimeHost interface does not support the .NET v1.x runtimes, 
//     the current possible values of the parameter are "v2.0.50727" and 
//     "v4.0.30319". Also, note that the “v” prefix is mandatory.
//   * pszAssemblyPath - The path to the Assembly to be loaded.
//   * pszClassName - The name of the Type that defines the method to invoke.
//
//   RETURN VALUE: HRESULT of the demo.
//
HRESULT RuntimeHostV4Demo2(PCWSTR pszVersion, PCWSTR pszAssemblyPath, 
    PCWSTR pszClassName)
{
    HRESULT hr;

    ICLRMetaHost *pMetaHost = NULL;
    ICLRRuntimeInfo *pRuntimeInfo = NULL;

    // ICorRuntimeHost and ICLRRuntimeHost are the two CLR hosting interfaces
    // supported by CLR 4.0. Here we demo the ICLRRuntimeHost interface that 
    // was provided in .NET v2.0 to support CLR 2.0 new features. 
    // ICLRRuntimeHost does not support loading the .NET v1.x runtimes.
    ICLRRuntimeHost *pClrRuntimeHost = NULL;

    // The static method in the .NET class to invoke.
    PCWSTR pszStaticMethodName = L"GetStringLength";
    PCWSTR pszStringArg = L"HelloWorld";
    DWORD dwLengthRet;

    // 
    // Load and start the .NET runtime.
    // 

    wprintf(L"Load and start the .NET runtime %s 
", pszVersion);

    hr = CLRCreateInstance(CLSID_CLRMetaHost, IID_PPV_ARGS(&pMetaHost));
    if (FAILED(hr))
    {
        wprintf(L"CLRCreateInstance failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Get the ICLRRuntimeInfo corresponding to a particular CLR version. It 
    // supersedes CorBindToRuntimeEx with STARTUP_LOADER_SAFEMODE.
    hr = pMetaHost->GetRuntime(pszVersion, IID_PPV_ARGS(&pRuntimeInfo));
    if (FAILED(hr))
    {
        wprintf(L"ICLRMetaHost::GetRuntime failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Check if the specified runtime can be loaded into the process. This 
    // method will take into account other runtimes that may already be 
    // loaded into the process and set pbLoadable to TRUE if this runtime can 
    // be loaded in an in-process side-by-side fashion. 
    BOOL fLoadable;
    hr = pRuntimeInfo->IsLoadable(&fLoadable);
    if (FAILED(hr))
    {
        wprintf(L"ICLRRuntimeInfo::IsLoadable failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    if (!fLoadable)
    {
        wprintf(L".NET runtime %s cannot be loaded
", pszVersion);
        goto Cleanup;
    }

    // Load the CLR into the current process and return a runtime interface 
    // pointer. ICorRuntimeHost and ICLRRuntimeHost are the two CLR hosting  
    // interfaces supported by CLR 4.0. Here we demo the ICLRRuntimeHost 
    // interface that was provided in .NET v2.0 to support CLR 2.0 new 
    // features. ICLRRuntimeHost does not support loading the .NET v1.x 
    // runtimes.
    hr = pRuntimeInfo->GetInterface(CLSID_CLRRuntimeHost, 
        IID_PPV_ARGS(&pClrRuntimeHost));
    if (FAILED(hr))
    {
        wprintf(L"ICLRRuntimeInfo::GetInterface failed w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Start the CLR.
    hr = pClrRuntimeHost->Start();
    if (FAILED(hr))
    {
        wprintf(L"CLR failed to start w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // 
    // Load the NET assembly and call the static method GetStringLength of 
    // the type CSSimpleObject in the assembly.
    // 

    wprintf(L"Load the assembly %s
", pszAssemblyPath);

    // The invoked method of ExecuteInDefaultAppDomain must have the 
    // following signature: static int pwzMethodName (String pwzArgument)
    // where pwzMethodName represents the name of the invoked method, and 
    // pwzArgument represents the string value passed as a parameter to that 
    // method. If the HRESULT return value of ExecuteInDefaultAppDomain is 
    // set to S_OK, pReturnValue is set to the integer value returned by the 
    // invoked method. Otherwise, pReturnValue is not set.
    hr = pClrRuntimeHost->ExecuteInDefaultAppDomain(pszAssemblyPath, 
        pszClassName, pszStaticMethodName, pszStringArg, &dwLengthRet);
    if (FAILED(hr))
    {
        wprintf(L"Failed to call GetStringLength w/hr 0x%08lx
", hr);
        goto Cleanup;
    }

    // Print the call result of the static method.
    wprintf(L"Call %s.%s("%s") => %d
", pszClassName, pszStaticMethodName, 
        pszStringArg, dwLengthRet);

Cleanup:

    if (pMetaHost)
    {
        pMetaHost->Release();
        pMetaHost = NULL;
    }
    if (pRuntimeInfo)
    {
        pRuntimeInfo->Release();
        pRuntimeInfo = NULL;
    }
    if (pClrRuntimeHost)
    {
        // Please note that after a call to Stop, the CLR cannot be 
        // reinitialized into the same process. This step is usually not 
        // necessary. You can leave the .NET runtime loaded in your process.
        //wprintf(L"Stop the .NET runtime
");
        //pClrRuntimeHost->Stop();

        pClrRuntimeHost->Release();
        pClrRuntimeHost = NULL;
    }

    return hr;
}