ICommand _canExecute problem

Question

Hi,

I have the following code and it won't compile because the compiler cannot determine the return type of my CanExecute method. Can someone help me as to what is wrong?

class ViewCommand : ICommand
    {
        #region ICommand Members

        public delegate Predicate<object> _canExecute(object param);
        private ICommand _Execute;

        _canExecute exe;

        public bool CanExecute(object parameter)
        {
            return exe == null ? true : exe(parameter); // <-- Error no implicit conversion between Predicate<object> and bool
        }

... // more code
}

Answer 1

The ICommand interface declares CanExecute as a function that takes a parameter and returns a bool.

Your _canExecute takes a parameter and returns a Predicate<object>

The way to invoke that would be to pass the parameter to the return value of exe

exe(parameter)(parameter);

I doubt that was your intention though.

I think you want to declare exe as a Predicate, and skip the delegate declaration.

private Predicate<object> exe;

This is what I think you want to look like:

class ViewCommand : ICommand
    {
        #region ICommand Members

        private ICommand _Execute;

        Predicate<object> exe;

        public bool CanExecute(object parameter)
        {
            return exe == null ? true : exe(parameter); // <-- Error no implicit conversion between Predicate<object> and bool
        }

... // more code
}