是否可以通过COM互操作转发代表？

Question

我有一节课:

public class A
{
public delegate void SetTextDel(string value);
public void Test()
{
      SetTextDel setText = someInterface.SetText;
      icom.Set(setText);
}
}

[ComVisible(true), Guid("81C99F84-AA95-41A5-868E-62FAC8FAC263"),   InterfaceType(ComInterfaceType.InterfaceIsDual)]
    public interface Icom
    {
        void Set(Delegate del);
    }

[ComVisible(true)]
    [Guid("6DF6B926-8EB1-4333-827F-DD814B868097")]
    [ClassInterface(ClassInterfaceType.None)]
    [ComDefaultInterface(typeof(Icom))]
    public class B : Icom
    {
         Set(Delegate del)
         {
              del.DynamicInvoke("some text");
         }
    }

我在Set(Delegate del)中获得了targetinvocation异常.有没有更好的方法来转发委托作为参数？或者我在这里犯了一些我没有看到的错误.我想做的是将someInterface.SetText这个方法作为参数传递.谢谢你的帮助.

Answer 1

以下作品:

public class A
{
    public delegate void SetTextDel(string value);

    void TestSetText(string value)
    {
        MessageBox.Show(value);
    }

    public void Test(Icom icom)
    {
        SetTextDel del = TestSetText;
        icom.Set(del);
    }
}

[ComVisible(true), Guid("81C99F84-AA95-41A5-868E-62FAC8FAC263"), InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface Icom
{
    void Set(Delegate del);
}

[ComVisible(true)]
[Guid("6DF6B926-8EB1-4333-827F-DD814B868097")]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(Icom))]
public class B : Icom
{
    public void Set(Delegate del)
    {
        del.DynamicInvoke("some text");
    }
}

private void buttonTest_Click(object sender, EventArgs e)
{
    var a = new A();
    var b = new B();

    a.Test(b);
}

接下来,如果您希望将回调函数从C++传递给Icom.Set,以下也可以使用:

[UnmanagedFunctionPointer(CallingConvention.StdCall)]
public delegate void SetTextDel([MarshalAs(UnmanagedType.BStr)] string value);

[ComVisible(true), Guid("81C99F84-AA95-41A5-868E-62FAC8FAC263"), InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface Icom
{
    void Set([MarshalAs(UnmanagedType.FunctionPtr)] SetTextDel del);
}

[ComVisible(true)]
[Guid("6DF6B926-8EB1-4333-827F-DD814B868097")]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(Icom))]
public class B : Icom
{
    public void Set(SetTextDel del)
    {
        del("some text");
    }
}

确保将您的C#和C++项目编译为32位代码.C++回调函数应该声明为:

static HRESULT __stdcall SetTextDelCallback(BSTR value)
{
    return S_OK;
}

最后,实现它的正确方法 IMO是简单地定义一个回调接口(如下ISetCallback所示)并传递一个实现这种接口的对象,而不是委托.ISetCallback可以用任何语言实现,无论是C#还是C++:

[ComVisible(true), Guid("2FE5D78D-D9F2-4236-9626-226356BA25E7")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface ISetCallback
{
    void OnSetText(string value);
}

public class A : ISetCallback
{
    public void OnSetText(string value) // ISetCallback
    {
        MessageBox.Show(value);
    }

    public void Test(Icom icom)
    {
        icom.Set(this);
    }
}

[ComVisible(true), Guid("81C99F84-AA95-41A5-868E-62FAC8FAC263"), InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface Icom
{
    void Set(ISetCallback callback);
}

[ComVisible(true)]
[Guid("6DF6B926-8EB1-4333-827F-DD814B868097")]
[ClassInterface(ClassInterfaceType.None)]
[ComDefaultInterface(typeof(Icom))]
public class B : Icom
{
    public void Set(ISetCallback callback)
    {
        callback.OnSetText("some text");
    }
}

private void buttonTest_Click(object sender, EventArgs e)
{
    var a = new A();
    var b = new B();

    a.Test(b);
}