RelayCommand不刷新执行/无法执行更改

Question

I'm newbee in mvvm (and mvvlight of course). I have 3 modelviews (a MainWindow which have a container, and another 2 modelviews (Login and Menu)). In the LoginModelView, when the user login is successfully, this call the MenuViewModel (With Messenger.Default) changing the page in the MainWindow container. All is alright until that, then i call a Message.Default.Send sending a object from LoginModelView to MenuModelView which is correctly listened, catching the object associed and executing the method associated (ConfiguraMenu) wich define a RelayCommand (checked line by line and the method is executed without any exception) but the problem is this RelayCommand is not working until i back to the LoginViewModel and i login again. I try CommandManager.InvalidateRequerySuggested() and is not working either.

This is the code for the LoginViewModel:

//This method is called when the user press the login button. No problem with this
        public void ActionVerificaUsuario()
        {
            Miusuario = db.getUsuario(Txtusuario, Txtpassword);
            if (Miusuario.esUsuario())
            {
                Messenger.Default.Send(new MoveToViewMessage(Page.MenuView));
                Messenger.Default.Send((UsuarioModel)Miusuario);
            }
        }

This code is for the MenuViewModel:

public RelayCommand AbreExeClaseCommand { get; private set; }

     public MenuViewModel()
        {
            Messenger.Default.Register<UsuarioModel>(this, usuario_recibido => {Miusuario = usuario_recibido;ConfiguraMenu(); });

        }

        private void ConfiguraMenu() {
            Mimenu = new MenuModel(Miusuario);
            AbreExeClaseCommand = new RelayCommand(() => { Messenger.Default.Send(new MoveToViewMessage(Page.NeverReachedView)); }, () => Mimenu.Sw_reportes);
            CommandManager.InvalidateRequerySuggested();            
            AbreExeClaseCommand.RaiseCanExecuteChanged();
        }

I tried to hardcode the CanExecute with true but the Execute is still without work until back and login again.

I hope you can help me (i'm scratching my head for various days with none result).

Answer 1

MvvmLight provides two different RelayCommand classes in two different namespaces:

• Galasoft.MvvmLight.Command
• Galasoft.MvvmLight.CommandWpf

Make sure, that you are using the correct namespace Galasoft.MvvmLight.CommandWpf in your WPF application.

There was a bug in MVVMLight, which resulted in not working CanExecute() behavior. They fixed it with the new .CommandWpf namespace in MVVMLight Version V5.0.2.

You can also check out this GalaSoft blog post and the change log for further information.

Answer 2

You try to bind the CanExecute to a propertie.

So my guess is you didn't use RaisePropertie Changed in this propertie. You must have something like:

        public class MenuModel : ViewModelBase
        {
            // Other pieces of code....

            private bool _sw_reportes;
            public bool Sw_reportes
            {
                get { return _sw_reportes; }
                set { _sw_reportes = value; 
                       RaisePropertyChanged(() => Sw_reportes); }
            }
        }