C# ArrayList 与 C++ Interop

Question

在 C# 中得到这个

public static ArrayList MyFct() 
{
  var x = new ArrayList();
  x.Add(5);
  return x
}

在使用 Interop 的 C++ 端，调用 Invoke_3() 后，我得到一个包含我的数组的 variant_t，但是我如何“提取“它？

（比如我想获取商品数量等）

Answer 1

这是一个 VARIANT (variant_t is a wrapper that comes from comdef.h / #import statement) that contains an IDispatch 参考，因此您可以使用 IDispatch 的方法，例如像这样（省略错误检查）：

variant_t v;
HRESULT hr = unk->GetList(&v); // get my VARIANT that contains an ArrayList reference

// get "Count" method dispid
LPOLESTR countName = (LPOLESTR)L"Count";
DISPID dispidCount;
hr = V_DISPATCH(&v)->GetIDsOfNames(IID_NULL, &countName, DISPATCH_METHOD, 0, &dispidCount);

DISPPARAMS dp = { nullptr, nullptr, 0, 0 };
variant_t count;
hr = V_DISPATCH(&v)->Invoke(dispidCount, IID_NULL, 0, DISPATCH_METHOD, &dp, &count, nullptr, nullptr);

// get "Item(i)" method dispid
LPOLESTR itemName = (LPOLESTR)L"Item";
DISPID dispidName;
hr = V_DISPATCH(&v)->GetIDsOfNames(IID_NULL, &itemName, DISPATCH_METHOD, 0, &dispidName);

for (int i = 0; i < V_I4(&count); i++)
{
    // build index as variant
    variant_t index(i);
    DISPPARAMS dpIndex = { &index, nullptr, 1, 0 };

    // get item(i)
    variant_t item;
    hr = V_DISPATCH(&v)->Invoke(dispidName, IID_NULL, 0, DISPATCH_METHOD, &dpIndex, &item, nullptr, nullptr);

    // item can be a scalar value
    // String => VT_BSTR, Int32 => VT_I4, etc.
    // or another ComVisible object => VT_DISPATCH, VT_UNKNOWN, etc.
}

C# ArrayList 与 C++ Interop

C# ArrayList with C++ Interop

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