c# - 从C++ DLL(使用 “Dllimport”从C#加载)中调用C#方法/函数。

在单个标题中恢复它有点困难，所以这就是我的情况。

我正在构建一个加载C++库的C#应用​​程序。
我从该C++ DLL调用函数。
但是我也想让我的C++ DLL从C#应用程序中调用函数(正在导入/运行它)...

这是一段使它更全面的代码:

// I'm importing functions from my native code
[DllImport(dllFilePath, CallingConvention = CallingConvention.Cdecl)]
public static extern int returnIntValue(int value);
[DllImport(dllFilePath, CallingConvention = CallingConvention.Cdecl)]
public static extern int returnIntArrValueAt(int[] values, int index);

// Here is the kind of code it should be
// [DllImport(dllFilePath, CallingConvention = CallingConvention.Cdecl)]
// public static extern void callCSharpFunction( FunctionPointer fctPointer );

main
{
    // I run the function
    int intValue1 =
        MyAddIn.returnIntValue(147852369);
    int intValue2 =
        MyAddIn.returnIntArrValueAt( new int[] { 9, 4, 3, 2, 1, 0 }, 5);

    // Here is an example function I use to call my C# func from C++
    // MyAddIn.returnIntValue( &myCSharpFunction );
}

// This is the method I'd like to call from my C++ imported library
static public void myCSharpFunction()
{
    MessageBox.Show("Called from C++ code !!");
}

因此，恢复:

C#代码导入我的C++ DLL

C#从C++ DLL运行函数

C++ DLL方法调用一个C#方法，该方法显示一个MessageBox(即)

最佳答案

这是我对this question的回答，与之类似。我的示例不对回调使用参数。由于您的参数是整数，因此您应该不会有任何问题。

基本上，Marshal.GetFunctionPointerForDelegate方法从委托(delegate)创建一个IntPtr。该委托(delegate)应具有与C++库中使用的函数指针相同的签名。

// This is the delegate type that we use to marshal
// a function pointer for C to use. You usually need
// to specify the calling convention so it matches the
// convention of your C library. The signature of this
// delegate must match the signature of the C function
// pointer we want to use.
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
delegate void FunctionPointer();

// This is the function we import from the C library.
[DllImport(dllFilePath)]
static extern void callCSharpFunction(IntPtr fctPointer);

// This is the placeholder for the function pointer
// we create using Marshal.GetFunctionPointerForDelegate
IntPtr FctPtr;

// This is the instance of the delegate to which our function
// pointer will point.
FunctionPointer MyFunctionPointer;

// This calls the specified delegate using the C library.
void CallFunctionPointer(FunctionPointer cb)
{
    // make sure the delegate isn't null
    if (null == cb) throw new ArgumentNullException("cb");

    // set our delegate place holder equal to the specified delegate
    MyFunctionPointer = cb;

    // Get a pointer to the delegate that can be passed to the C library
    FctPtr = Marshal.GetFunctionPointerForDelegate(MyFunctionPointer );

    // call the imported function with that function pointer.
    callCSharpFunction(FctPtr);
}