将 C# 字符串传递给非托管 C++ DLL

我有一个简单的应用程序，它加载一个非托管 dll 并从 C# 向它传递一些字符串值。但在 C++ dll 应用程序中，我收到异常 :: 试图访问读/写保护的内存。我的 DLL 导入如下所示：

[DllImport("X.dll", CallingConvention = CallingConvention.Cdecl) ]
public static extern int
DumpToDBLogFile([MarshalAs(UnmanagedType.I4)]int loggingLevel,
                [MarshalAs(UnmanagedType.I4)]int jobId,
                int threadId,
                [MarshalAs(UnmanagedType.LPStr)]string procName,
                [MarshalAs(UnmanagedType.LPStr)]string message);

C++ 声明就像

extern "C"    
__declspec(dllexport) int DumpToDBLogFile( int loggingLevel, int jobId, int threadId, string procName, string message )
{
    //access strings..
}

请帮助！！！

string != LPStr

try:

extern "C"
__declspec(dllexport) int DumpToDBLogFile( int loggingLevel, int jobId, int threadId, char* procName, char* message ) { //access strings..

}