WPF disable command for a while it running

Question

I need to disable button for a while it running. I have this code:

RelayCommand.cs This is my command class.

class RelayCommand : ICommand
{
    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {
    }

    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
        {
            throw new ArgumentNullException("execute");
        }

        _execute = execute;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameter)
    {
        _execute(parameter);
    }
}

MainWindowViewModel.cs This is my command for binding.

private RelayCommand _getTextCommand;
public ICommand GetTextCommand
{
    get
    {
        if (_getTextCommand == null)
        {
            _getTextCommand = new RelayCommand(
                param => this.GetText(param),
                param => true
                );
        }

        return _getTextCommand;
    }
}

MainWindow.xaml This is XAML code where i bind my command.

<Button x:Name="getTextButton" Command="{Binding GetTextCommand}" CommandParameter="{Binding ElementName=textTypeSelector, Path=SelectedIndex}"/>

This is the code i am launching in command:

public async void GetText(object o)
{
    await Task.Factory.StartNew(() =>
    {
        // code
    });
}

score 7 · Accepted Answer · edited Jun 07 '16 at 06:24

Try this: add a boolean property in view model and implement INotifyPropertyChanged in view model

    private bool isEnable = true;

    public bool IsEnable 
    {
        get { return isEnable; }
        set
        {
            isEnable = value; 
            NotifyPropertyChanged();
        } 
    }

    public async void GetText(object o)
    {
        await Task.Factory.StartNew(() =>
        {

            IsEnable = false;
        });
        IsEnable = true;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

Bind it to button IsEnable property

<Button x:Name="abc"
                Command="{Binding GetTextCommand}"
                IsEnabled="{Binding IsEnable}" />

Set IsEnable whereever you want.

Jehof · Answer 2 · 2014-03-13T09:38:01.750

3

Add a boolean to your ViewModel to indicate that the command is executing and set the boolean in your GetText() method.

private bool _isRunning = false;

public async void GetText(object o)
{
    await Task.Factory.StartNew(() =>
    {
        _isRunning = true;
        CommandManager.InvalidateRequerySuggested(); 
        // code
        _isRunning = false;
        CommandManager.InvalidateRequerySuggested();
    });
}

public bool CanGetText(object o){
  return ! _isRunning;
}

Then change your RelayCommand to the following

_getTextCommand = new RelayCommand(this.GetText,CanGetText);

edited Mar 13 '14 at 09:38

answered Mar 13 '14 at 09:02

Jehof

34,674
10
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155

it is good, but 1 issue. After code is done, the button do not sets in enabled state. It sets in enabled state after clicking on it. How it can be solved? – BJladu4 Mar 13 '14 at 09:33
@user2932802 ok, i think you need to use a CanExecute method in your ViewModel. I´ll update the code. Normally should CommandManager.InvalidateRequerySuggested() check and enable the button state – Jehof Mar 13 '14 at 09:37
you can shorten it with `new RelayCommand(this.GetText, CanGetText);` – default Mar 13 '14 at 09:41
update. if i minimize window or click in random place on it, button will be enabled – BJladu4 Mar 13 '14 at 09:56

score 2 · Answer 3 · answered Mar 13 '14 at 09:02

2

The problem is that you are passing true for the CanExecute delegate. Pass it a method that will execute every time it needs evaluation, and within that method you can test to see whether the Command should be executable or otherwise.

answered Mar 13 '14 at 09:02

stevethethread

2,524
2
30
29

One thing I would think about is looking at using RX with ICommand. I have been reliably informed that it helps eliminate some of the issues you see with buttons being disabled or otherwise based on CanExecute. See here http://stackoverflow.com/questions/1763411/reactive-extensions-rx-mvvm and here https://github.com/reactiveui/reactiveui – stevethethread Mar 14 '14 at 14:12

score 2 · Answer 4 · answered Mar 20 '14 at 16:05

Here is an implementation that I'm using. It doesn't need an additional property in the ViewModel.

public sealed class AsyncDelegateCommand : ICommand
{
   private readonly Func<bool> _canExecute;
   private readonly Func<Task> _executeAsync;
   private Task _currentExecution;

   public AsyncDelegateCommand(Func<Task> executeAsync)
      : this(executeAsync, null)
   {
   }

   public AsyncDelegateCommand(Func<Task> executeAsync, Func<bool> canExecute)
   {
      if (executeAsync == null) throw new ArgumentNullException("executeAsync");
      _executeAsync = executeAsync;
      _canExecute = canExecute;
   }

   public event EventHandler CanExecuteChanged
   {
      add { CommandManager.RequerySuggested += value; }
      remove { CommandManager.RequerySuggested -= value; }
   }

   public bool CanExecute(object parameter)
   {
      if (_currentExecution != null && !_currentExecution.IsCompleted)
      {
         return false;
      }

      return _canExecute == null || _canExecute();
   }

   public async void Execute(object parameter)
   {
      try
      {
         _currentExecution = _executeAsync();
         await _currentExecution;
      }
      finally
      {
         _currentExecution = null;
         CommandManager.InvalidateRequerySuggested();
      }
   }
}

WPF disable command for a while it running

4 Answers4