The following works:
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);
}
Next, if you're looking to pass a callback function from C++ to Icom.Set
, the following would work too:
[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");
}
}
Make sure to compile both of your C# and C++ projects as 32-bit code. The C++ callback function should be declared as such:
static HRESULT __stdcall SetTextDelCallback(BSTR value)
{
return S_OK;
}
Finally, the proper way to implement this, IMO, is to simply define a callback interface (like ISetCallback
below) and pass an object implementing such interface, rather than a delegate. ISetCallback
can be implemented in any language, either C# or 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);
}