c# unmanaged PInvoke AccessViolation

Question

我有C++DLL。当从 C# 中的此 DLL 调用方法时，会引发访问冲突。我的代码中有什么问题？有人可以帮助我吗？C++ 标题部分：

typedef PVOID X_HANDLE;
XREADER_API BOOL ReaderOpen(X_HANDLE *pxHandle);
XREADER_API BOOL ReaderReceiveW26(X_HANDLE xHandle, LPVOID pBuffer, DWORD nBufferSize);

工作示例第 C++ 部分：

X_HANDLE hReader;
unsigned char xKeyBuffer[3];
ReaderOpen(&hReader);
ReaderReceiveW26(hReader,xKeyBuffer,sizeof(xKeyBuffer));

我的 C# 代码：

[DllImport("reader.dll", CallingConvention = CallingConvention.Cdecl, SetLastError = true)]
public static extern bool ReaderOpen(IntPtr reference);
[DllImport("reader.dll", CallingConvention = CallingConvention.Cdecl, SetLastError = true)]
public static extern bool ReaderReceiveW26(IntPtr hReader, IntPtr pBuffer, uint xKeyBuffer);
    static void Main(string[] args)
    {
        byte[] received = new byte[3];
        IntPtr unmanagedPointer = Marshal.AllocHGlobal(received.Length);
        Marshal.Copy(received, 0, unmanagedPointer, received.Length);
        IntPtr hReader = Marshal.AllocHGlobal(sizeof(uint));
        var qqq = uint.Parse((Marshal.SizeOf(typeof(byte)) * received.Length).ToString());
        ReaderOpen(hReader);
        while (true)
        {
            if (ReaderReceiveW26(hReader, unmanagedPointer, qqq))
            {
                Console.WriteLine("!");
            }
        }
    }

AccessViolation throw at ReaderReceiveW26（hReader， unmanagedPointer， qqq）

感谢您的耐心等待！

Answer 1

感谢 Hast Passant 评论！如果我们想使用由非托管代码编辑的 IntPtr 或 smth，我们需要使用

out paramName

对于PVOID，我们可以传递真正的c#类型。

工作示例：

[DllImport("reader.dll", CallingConvention = CallingConvention.Cdecl, SetLastError = true)]
public static extern bool ReaderOpen(out IntPtr reference);
[DllImport("reader.dll", CallingConvention = CallingConvention.Cdecl, SetLastError = true)]
public static extern bool ReaderReceiveW26(IntPtr hReader, byte[] pBuffer, uint xKeyBuffer);