我从 C++ 非托管代码调用 C# 方法。我在从数组中返回的类实例获取值时遇到问题。
我稍微简化了代码
这是有问题的方法。
[return: MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_UNKNOWN)]
public ScOrder[] GetOrders()
{
return new ScOrder[] {
(new ScOrder(1),
(new ScOrder(2)
};
}
这是 IScOrder 接口
[ComVisible(true)]
[Guid("B2B134CC-70A6-43CD-9E1E-B3A3D9992C3E")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IScOrder
{
long GetQuantity();
}
这是 ScOrder 实现
[ComVisible(true)]
[Guid("F739759E-4D00-440E-B0B7-69AAF97FCB6D")]
[ClassInterface(ClassInterfaceType.None)]
public class ScOrder
{
private long quantity = 0;
public ScOrder() {}
public ScOrder(long quantity)
{
this.quantity = quantity;
}
public long GetQuantity()
{
return this.quantity;
}
}
这是 C++ 代码,在我的 Zdeslav Vojkovic 的帮助下先前的请求 https://stackoverflow.com/questions/12412533/convert-cast-safearray-of-iunknowns-to-an-iterable-array-of-interface-pointers/12420569#12420569。问题已在评论中描述
- 我没有使用 ATL 也没有使用 MFC。
- C++ tlb 文件是通过 regasm 生成的。
COM 初始化和调用 GetOrders 方法效果很好
IScProxyPtr iPtr;
CoInitialize(NULL);
iPtr.CreateInstance(CLSID_ScProxy);
SAFEARRAY* orders;
iPtr->GetOrders(&orders);
LPUNKNOWN* punks;
HRESULT hr = SafeArrayAccessData(orders, (void**)&punks);
if(SUCCEEDED(hr))
{
long lbound, ubound;
SafeArrayGetLBound(orders, 1, &lbound);
SafeArrayGetUBound(orders, 1, &ubound);
long elements = ubound - lbound + 1;
for(int i=0;i<elements;i++)
{
LPUNKNOWN punk = punks[i]; //the punk seems valid
IScOrderPtr order(punk); //unfortunatelly, "order" now points to {0x00000000}
//subsequent attempt to get the value will fail
long quantity = 0;
HRESULT procCall;
//GetQuantity will throw an exception
procCall = order->GetQuantity((long long *)q);
}
SafeArrayUnaccessData(orders);
}
SafeArrayDestroy(orders);
感谢 Zdeslav,我发现我可以在 order(punk) 中进行调试:
IScOrderPtr order(punk);
所以我走进了秩序(朋克)去看看那里发生了什么。我进入了“comip.h”
// Constructs a smart-pointer from any IUnknown-based interface pointer.
//
template<typename _InterfaceType> _com_ptr_t(_InterfaceType* p)
: m_pInterface(NULL)
{
HRESULT hr = _QueryInterface(p);
...然后我进入了 _QueryInterface(p) 实现,也在 comip.h 中
// Performs a QI on pUnknown for the interface type returned
// for this class. The interface is stored. If pUnknown is
// NULL, or the QI fails, E_NOINTERFACE is returned and
// _pInterface is set to NULL.
//
template<typename _InterfacePtr> HRESULT _QueryInterface(_InterfacePtr p) throw()
{
HRESULT hr;
// Can't QI NULL
//
if (p != NULL) {
// Query for this interface
//
Interface* pInterface;
hr = p->QueryInterface(GetIID(), reinterpret_cast<void**>(&pInterface));
现在的问题是,返回的“hr”值是 E_NOINTERFACE ...这是不对的。
我不是 C++ 或 COM 专家...请帮助:)