Team issue. How to enable the command button

Question

My code is here →

public class Player:INotifyPropertyChanging
{
        string addressBar;
        public string Url
        {
            get {

                return addressBar;
            }
            set { addressBar = value; OnPropertyChanged("Url"); }
        }
        public Regex regVillage = new Regex(@"\?doc=\d+&sys=[a-zA-Z0-9]{2}");

        RelayCommand _AddAttackTask;
        public ICommand AddAttackTask
        {
            get {
                if (_AddAttackTask == null)
                {
                    _AddAttackTask = new RelayCommand(param =>
                    {

                    }, param => this.CanAttack);
                }
                return _AddAttackTask;
            }
        }

        public Boolean CanAttack
        {
            get{
                if (Url == null) return false;
                return regVillage.IsMatch(Url);
            }            
        }
}

On xaml, I have a text box and a button. The text field is anchored url, the button is anchored AddAttackTask. When I change the value of the text box, Url is changed. The main goal is to change the URL, the enable or disable button. But the button is always off.

I get the RelayCommand class from a WPF application with a Model-View-ViewModel design pattern

What is wrong in my code?

Fix the binding of my team!

Answer 1

I found it myself.

Must call a function CommandManager.InvalidateRequerySuggested();after changing a property

public string Url
        {
            get {

                return addressBar;
            }
            set { addressBar = value; OnPropertyChanged("Url"); 
                  CommandManager.InvalidateRequerySuggested();
            }
        }