从C#访问COM vtable

Question

在C#中是否有任何方法可以访问COM对象的虚方法表以获取函数的地址？

Answer 1

在经过大量搜索并拼凑出不同的部分解决方案后,我想出了如何做到这一点.

首先,您需要为要尝试访问的对象定义COM coclass:

[ComImport, Guid("..."), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface ISomeCOMInterface
{
   // Define interface methods here, using PInvoke conversion between types
}

接下来,您需要实例化COM对象.有几种方法可以做到这一点.由于我对DirectSound感兴趣,我用过:

[DllImport("dsound.dll", EntryPoint = "DirectSoundCreate", ...]
static extern void DirectSoundCreate(IntPtr GUID, [Out, MarshalAs(UnmanagedType.Interface)] out IDirectSound directSound, IntPtr pUnkOuter);

IDirectSound directSound;
DirectSoundCreate(IntPtr.Zero, out directSound, IntPtr.Zero);

因为我现在有了COM对象,所以我可以使用Hans的建议Marshal.GetComInterfaceForObject():

IntPtr comPtr = Marshal.GetComInterfaceForObject(directSound, typeof(IDirectSound));
IntPtr vTable = Marshal.ReadIntPtr(comPtr);

作为额外的奖励,您可以像这样迭代vtable函数:

int start = Marshal.GetStartComSlot(typeof(IDirectSound));
int end = Marshal.GetEndComSlot(typeof(IDirectSound));

ComMemberType mType = 0;
for (int i = start; i <= end; i++)
{
    System.Reflection.MemberInfo mi = Marshal.GetMethodInfoForComSlot(typeof(IDirectSound), i, ref mType);
    Console.WriteLine("Method {0} at address 0x{1:X}", mi.Name, Marshal.ReadIntPtr(vTable, i * Marshal.SizeOf(typeof(IntPtr))).ToInt64());
}

额外阅读/参考:

• http://msdn.microsoft.com/en-us/library/aa645736(VS.71).aspx [关于COM coclass声明的信息]
• http://www.codeproject.com/KB/COM/com_in_c1.aspx [关于VTables和COM的信息]
• http://naudio.codeplex.com/ [特定于DirectSound COM接口的信息]