Question

I’m trying to make this extension method. Getting an error on the casts saying ‘Cannot convert type T to MouseEventArgs’. Shouldn’t I be able to upcast the object (since MouseEventArgs : InputEventArgs)?

In case you are curious, I am using this to share event handlers between Mouse and Touch events by just using the base InputEventArgs in the handler method.

    public static class InputEventArgsExtensions
    {
        public static Point GetPosition<T>(this T e, IInputElement obj)
            where T : InputEventArgs
        {
            if (e is MouseEventArgs)
                return ((MouseEventArgs)e).GetPosition(obj);
            else if (e is TouchEventArgs)
                return ((TouchEventArgs)e).GetTouchPoint(obj).Position;

            return new Point();
        }
    }

Answer 1

I tried doing this and it worked for me.

    public static class InputEventArgsExtensions
    {
        public static Point GetPosition<T>(this T e, IInputElement obj)
            where T : InputEventArgs
        {
            if (e is MouseEventArgs)
                return (e as MouseEventArgs).GetPosition(obj);
            else if (e is TouchEventArgs)
                return (e as TouchEventArgs).GetTouchPoint(obj).Position;

            return new Point();
        }
    }