C#•9h ago

Managed callback to native code (reverse p/invoke)

If I pass a managed callback to native code, do I need to pin the stored delegate so it does not get moved to a new memory address or is this handled by the runtime?

public class MyTestClass
{
    private delegate void NativeTestCallback(int num);

    [DllImport("TestNative")]
    private static extern void NativeFunc(NativeTestCallback callback);

    private NativeTestCallback _callback;
    public MyTestClass()
    {
        // do I need to pin this?
        _callback = TestCallback;
        NativeFunc(_callback);
    }

    private void TestCallback(int num)
    {

    }
}

public class MyTestClass
{
    private delegate void NativeTestCallback(int num);

    [DllImport("TestNative")]
    private static extern void NativeFunc(NativeTestCallback callback);

    private NativeTestCallback _callback;
    public MyTestClass()
    {
        // do I need to pin this?
        _callback = TestCallback;
        NativeFunc(_callback);
    }

    private void TestCallback(int num)
    {

    }
}

4 Replies

Mąż Zuzanny Harmider Szczęście•8h ago

all you need to do is make it static i think

nathanAjacobsOP•8h ago

Yeah I could, but I'm curious specifically about the semantics of an instanced callback. For example, I could have an unmanaged and managed representation of a class and have an instance id to track it between creation and disposal on the native side

Mąż Zuzanny Harmider Szczęście•8h ago

then ig u have to pin it, not really sure tho

nathanAjacobsOP•6h ago

Yeah that's what I'm thinking too, but wanted to get confirmation

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Managed callback to native code (reverse p/invoke)

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