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title WRL integration (C++/CX) | Microsoft Docs
ms.custom
ms.date 01/22/2017
ms.technology cpp-windows
ms.reviewer
ms.suite
ms.tgt_pltfrm
ms.topic article
ms.assetid 3ad43894-c574-477c-ad3e-240301f381d4
caps.latest.revision 9
author ghogen
ms.author ghogen
manager ghogen

WRL integration (C++/CX)

You freely can mix WRL code with [!INCLUDEcppwrl] ([!INCLUDEcppwrl_short]) code. In the same translation unit, you can use objects declared with WRL handle-to-object (^) notation and [!INCLUDEcppwrl_short] smart pointer (ComPtr<T>) notation. However, you must manually handle return values, and [!INCLUDEcppwrl_short] HRESULT error codes and WRL exceptions.

[!INCLUDEcppwrl_short] development

For more information about authoring and consuming [!INCLUDEcppwrl_short] components, see Windows Runtime C++ Template Library (WRL).

Example

The following code snippet demonstrates using WRL and [!INCLUDEcppwrl_short] to consume [!INCLUDEwrt] classes and examine a metadata file.

master

The example taken from a code snippet in the Building Windows Store apps forum. The author of this code snippet offers the following disclaimers and stipulations:

  1. C++ doesn't provide specific APIs to reflect on [!INCLUDEwrt] types, but Windows metadata files (.winmd) for a type are fully compliant with CLR metadata files. Windows provides the new metadata discovery APIs (RoGetMetaDataFile) to get to the .winmd file for a given type. However, these APIs are of limited use to C++ developers because you can't instantiate a class.

  2. After the code is compiled, you'll also need to pass Runtimeobject.lib and Rometadata.lib to the Linker.

  3. This snippet is presented as-is. While it is expected to work correctly, it possibly can contain errors.

  
#include <hstring.h>  
#include <cor.h>  
#include <rometadata.h>  
#include <rometadataresolution.h>  
#include <collection.h>  
  
namespace ABI_Isolation_Workaround {  
    #include <inspectable.h>  
    #include <WeakReference.h>  
}  
using namespace ABI_Isolation_Workaround;  
#include <wrl/client.h>  
  
using namespace Microsoft::WRL;  
using namespace Windows::Foundation::Collections;  
  
IVector<String^>^ GetTypeMethods(Object^);  
  
MainPage::MainPage()  
{  
    InitializeComponent();  
  
    Windows::Foundation::Uri^ uri = ref new Windows::Foundation::Uri("http://buildwindows.com/");  
    auto methods = GetTypeMethods(uri);  
  
    std::wstring strMethods;  
    std::for_each(begin(methods), end(methods), [&strMethods](String^ methodName) {  
        strMethods += methodName->Data();  
        strMethods += L"\n";  
    });  
  
    wprintf_s(L"%s\n", strMethods.c_str());  
}  
  
IVector<String^>^ GetTypeMethods(Object^ instance)  
{  
    HRESULT hr;  
    HSTRING hStringClassName;  
    hr = instance->__cli_GetRuntimeClassName(reinterpret_cast<__cli_HSTRING__**>(&hStringClassName)); // internal method name subject to change post BUILD  
    if (FAILED(hr))  
        __cli_WinRTThrowError(hr); // internal method name subject to change post BUILD  
    String^ className = reinterpret_cast<String^>(hStringClassName);   
  
    ComPtr<IMetaDataDispenserEx> metadataDispenser; ComPtr<IMetaDataImport2> metadataImport; hr = MetaDataGetDispenser(CLSID_CorMetaDataDispenser, IID_IMetaDataDispenser, (LPVOID*)metadataDispenser.GetAddressOf());  
    if (FAILED(hr))  
        __cli_WinRTThrowError(hr); // internal method name subject to change post BUILD  
  
    HSTRING hStringFileName;  
    mdTypeDef typeDefToken;   
    hr = RoGetMetaDataFile(hStringClassName, metadataDispenser.Get(), &hStringFileName, &metadataImport, &typeDefToken);  
    if (FAILED(hr))  
        __cli_WinRTThrowError(hr); // internal method name subject to change post BUILD  
    String^ fileName = reinterpret_cast<String^>(hStringFileName);  
  
    HCORENUM hCorEnum = 0;  
    mdMethodDef methodDefs[2048];  
    ULONG countMethodDefs = sizeof(methodDefs);  
    hr = metadataImport->EnumMethods(&hCorEnum, typeDefToken, methodDefs, countMethodDefs,  &countMethodDefs);  
    if (FAILED(hr))  
        __cli_WinRTThrowError(hr); // internal method name subject to change post BUILD  
  
    wchar_t methodName[1024];  
    ULONG countMethodName;  
    std::wstring strMethods;  
    Vector<String^>^ retVal = ref new Vector<String^>();  
  
    for(int i = 0; i < countMethodDefs; ++i)  
    {  
        countMethodName = sizeof(methodName);  
        hr = metadataImport->GetMethodProps(methodDefs[i], nullptr, methodName, countMethodName, &countMethodName, nullptr, nullptr, nullptr, nullptr, nullptr);  
        if (SUCCEEDED(hr))  
        {  
            methodName[ countMethodName ] = 0;  
            retVal->Append(ref new String(methodName));  
        }  
    }  
    return retVal;  
}

See Also

Interoperating with Other Languages