Swizzling Method in #xamarin

gistfile1.txt

 [DllImport ("/usr/lib/libobjc.dylib")]
    extern static IntPtr class_getInstanceMethod (IntPtr classHandle, IntPtr Selector);
    [DllImport ("/usr/lib/libobjc.dylib")]
    extern static Func<IntPtr,IntPtr,IntPtr> method_getImplementation (IntPtr method);
    [DllImport ("/usr/lib/libobjc.dylib")]
    extern static IntPtr imp_implementationWithBlock (ref BlockLiteral block);
    [DllImport ("/usr/lib/libobjc.dylib")]
    extern static void method_setImplementation (IntPtr method, IntPtr imp);

    static Func<IntPtr,IntPtr,IntPtr> original_impl;

    void HijackWillMoveToSuperView ()
    {
        var method = class_getInstanceMethod (new UIView ().ClassHandle, new Selector ("willMoveToSuperview:").Handle);
        original_impl = method_getImplementation (method);
        var block_value = new BlockLiteral ();
        CaptureDelegate d = MyCapture;
        block_value.SetupBlock (d, null);
        var imp = imp_implementationWithBlock (ref block_value);
        method_setImplementation (method, imp);
    }

    delegate void CaptureDelegate (IntPtr block, IntPtr self, IntPtr uiView);

    [MonoPInvokeCallback (typeof (CaptureDelegate))]
    static void MyCapture (IntPtr block, IntPtr self, IntPtr uiView)
    {
        Console.WriteLine ("Moving to: {0}", Runtime.GetNSObject (uiView));
        original_impl (self, uiView);
        Console.WriteLine ("Added");
    }