Xamarin forms Commanding CanExecute does not update Button IsEnabled - xamarin

Question

I'm trying to apply a style to a button which has been disabled by a command.
I assumed the IsEnabled state was the property that was being triggered by the canexecutechanged event but it seems it does not.
What Button Property is being affected and can I hook into this event so that I can provide a style to the button?

Answer 1

In your viewmodel you can add a property that will lead to enable or disable its buttons. follows an example below.
public Command FacebookLoginCommand { get; set; }
private bool _IsBusy;
public override bool IsBusy
{
get
{
return _IsBusy;
}
set
{
_IsBusy = value;
OnPropertyChanged();
FacebookLoginCommand?.ChangeCanExecute();
GoogleLoginCommand?.ChangeCanExecute();
}
}
public LoginViewModel(IUserDialogs dialogs) : base(dialogs)
{
FacebookLoginCommand = new Command(async () =>
{
using (Dialogs.Loading("Carregando"))
{
IsBusy = true;
await Task.Run(() => new FacebookLoginService(Dialogs).Logar());
await Task.Run(() => Task.Delay(TimeSpan.FromSeconds(3)));
IsBusy = false;
}
}, CanExecute());
private Func<bool> CanExecute()
{
return new Func<bool>(() => !IsBusy);
}
}

Answer 2

Here is the example to login when username length 11 and password at least one.
public class MainViewModel : BaseViewModel
{
public Command LoginIn { get; set; }
public MainViewModel()
{
LoginIn = new Command(async () => await SignIn(), (() => CanExecuteLogin));
}
private string _password;
private string _username;
public string UserName
{
get => _username;
set
{
SetProperty(ref _username, value, nameof(UserName));
SetProperty(ref _canExecuteLogin, IsExecutable(), nameof(CanExecuteLogin));
LoginIn?.ChangeCanExecute();
}
}
public string Password
{
get => _password;
set
{
SetProperty(ref _password, value, nameof(Password));
SetProperty(ref _canExecuteLogin, IsExecutable(), nameof(CanExecuteLogin));
LoginIn?.ChangeCanExecute();
}
}
private bool _canExecuteLogin;
public bool CanExecuteLogin
{
get => _canExecuteLogin;
set => SetProperty(ref _canExecuteLogin, value, nameof(CanExecuteLogin));
}
public bool IsExecutable()
{
if (UserName != null && _password != null)
{
if (UserName.Length == 11 && _password.Length > 0)
return true;
}
return false;
}
private async Task SignIn()
{ //Login Code here }
}