将数组移交给 C# 中动态加载的 C++ DLL 时出现 System.AccessViolationException

Question

我在 C# 程序中动态加载最初用 C++ 编写的 DLL，并将数组作为参数传递，如下所示：

// That's only for being able to load the DLL dynamically during runtime
[DllImport(@"C:\Windows\System32\kernel32.dll", EntryPoint = "LoadLibrary")]
public static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string dllToLoad);

[DllImport(@"C:\Windows\System32\kernel32.dll", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)]
public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);

[DllImport(@"C:\Windows\System32\kernel32.dll", EntryPoint = "FreeLibrary")]
public static extern bool FreeLibrary(IntPtr hModule);

// Delegate with function signature for the DISCON function
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
[return: MarshalAs(UnmanagedType.U4)]
delegate void DisconDelegate(float[] arr);

static void Main(string[] args){
   // Load DLL
   IntPtr _dllhandle = IntPtr.Zero;
   DisconDelegate _discon = null;
   string dllPath = @"D:\myProject\Trivial_discon.dll";

    _dllhandle = LoadLibrary(dllPath);
    var discon_handle = GetProcAddress(_dllhandle, "DISCON");
   _discon = (DisconDelegate)Marshal.GetDelegateForFunctionPointer(discon_handle, typeof(DisconDelegate));

   // create the array and change it after its initialization
   float[] arr = new float[] { 5, 6, 7 };
   arr[0] = 7;

   _discon(arr);
}

请注意，我在初始化后再次更改arr[0] = 7; 数组的条目。这将返回以下错误：System.AccessViolationException H结果=0x80004003 Message=试图读取或写入受保护的内存。这通常表明其他内存已损坏。 来源= 堆栈跟踪：

但是，如果我离开 arr[0] = 7;，它会起作用。

所以我想知道：为什么在这种情况下初始化之后更改数组的条目会有问题？我该如何解决这个问题，即如何在初始化后更改数组的条目并仍然能够将其作为参数传递给 DLL？

Answer 1

您需要将数组从托管内存转换为非托管内存。尝试关注

       static void Main(string[] args)
        {

            Data data = new Data();
            data.arr = new float[] { 5, 6, 7 };
            IntPtr arrPtr = Marshal.AllocHGlobal(data.arr.Length * sizeof(float));
            Marshal.StructureToPtr(data, arrPtr, true);
        }
        [StructLayout(LayoutKind.Sequential)]
        public struct Data
        {

            public float[] arr;
        }