在 C# 中编组非托管变量

Question

我正在我的 C# 代码中导入非托管 dll。 .h 文件描述了如下所示的方法

DLL_API int __stdcall SetConfiguration(IN char* configuration);

DLL_API int  __stdcall GetErrorMessage_UTF16(
    INOUT int* errorGroup, 
    INOUT char* errorCode, /*It must be allocated by the caller and its length must be at least 10 bytes, otherwise the function will crash*/
    INOUT wchar_t *messageText, 
    IN int bufferLength);

我已成功调用 SetConfiguration 方法

[DllImport(DllPath, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
private static extern int SetConfiguration([In] MarshalAs(UnmanagedType.LPStr)] string configuration);

提供一个简单的 C# 字符串即可完成工作。

现在我正在尝试 GetErrorMessage_UTF16 方法但没有成功。那么，如何分配 errorCode 的长度以及如何声明 wchar_t *messageText 变量？

我试过类似的方法，但似乎不起作用

[DllImport(DllPath, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
private static extern int GetErrorMessage_UTF16(
    [In, Out] int errorGroup, 
    [In, Out] [MarshalAs(UnmanagedType.LPStr)] string errorCode, 
    [In, Out] [MarshalAs(UnmanagedType.LPStr)] StringBuilder messageText, 
    [In] int bufferLength);

无论我试过什么，我都会得到

Exception thrown at 0x0f5d1235 (Mydll.dll) in Mydll.exe: 0xc0000005: Access violation writing location 0x067d1000

If there is a handler for this exception, the program may be safely continued.

Answer 1

好的，我找到答案了

[DllImport(DllName, EntryPoint = "GetErrorMessage_UTF16", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
public static extern int GetErrorMessage_UTF16(out int errorGroup, IntPtr errorCode, IntPtr messageText, int bufferLength);

为errorCode和messageText创建一个指针，然后分配大小。

IntPtr errorCode = Marshal.AllocHGlobal(10);
IntPtr messageText = Marshal.AllocHGlobal(someBufferLength * sizeof(char));

不要忘记在不需要变量时释放已分配的 space。

在 C# 中编组非托管变量

Marshal unmanaged variables in c#

c#

dllimport

unmanaged

wchar-t

interopservices