WPF IsEnabled Grid

Question

I want to get my grid disabled when my property is Null and enabled when is Not null.

In my .XAML :

  <Grid Grid.Row="2" IsEnabled="{Binding ElementName=dgCustomers, Path=SelectedItem}">
      <my:ProductsHistoryDetailView />
  </Grid>

In my ViewModel.cs :

    public ProductHistory SelectedItem
    {
        get { return _SelectedItem; }
        set
        {
            if (_SelectedItem != value)
            {
                _SelectedItem = value;
                RaisePropertyChanged(() => SelectedItem);
            }
        }
    }

Answer 1

You should add an extra property to your viewmodel.

    public bool IsGridEnabled
    {
        get 
          { 
             return this.SelectedItem != null;
          }
    }

<Grid Grid.Row="2" IsEnabled="{Binding IsGridEnabled}">
     <my:ProductsHistoryDetailView />
</Grid>

And when your SelectedItem changes, call the OnPropertyChanged event for IsGridEnabled:

public ProductHistory SelectedItem
{
    get { return _SelectedItem; }
    set
    {
        if (_SelectedItem != value)
        {
            _SelectedItem = value;
            RaisePropertyChanged(() => SelectedItem);
            RaisePropertyChanged(() => IsGridEnabled);
        }
    }
}

Answer 2

Use a Style Trigger to change the Enabled Property instead of trying to bind it directly

<Grid Grid.Row="2">
    <Grid.Style>
        <Style TargetType="Grid">
           <Setter Property="IsEnabled" Value="True"/>
           <Style.Triggers>
               <DataTrigger Binding="{Binding ElementName=dgCustomers, Path=SelectedItem"}" Value={x:Null}>
                    <Setter Property="IsEnabled" Value="False"/>
               </DataTrigger>
           </Style.Triggers>            
        </Style>
    </Grid.Style>
</Grid>

Answer 3

You could use an IValueConverter:

<Grid Grid.Row="2" IsEnabled="{Binding 
    ElementName=dgCustomers, Path=SelectedItem, 
    Converter={StaticResource NullToFalseConverter}">

public class NullToFalseConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value == null ? false : true;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Alternatively, it might be easier to add another property IsSelected to your view model, which you could bind directly to IsEnabled:

public bool IsSelected
{
    get { return _isSelected; }
    set
    {
        if (_isSelected != value)
        {
            _isSelected = value;
            RaisePropertyChanged(() => IsSelected);
        }
    }
}

public ProductHistory SelectedItem
{
    get { return _SelectedItem; }
    set
    {
        if (_SelectedItem != value)
        {
            _SelectedItem = value;
            RaisePropertyChanged(() => SelectedItem);
        }
        IsSelected = value != null;
    }
}

Answer 4

Please make sure your selectebitem has a valid value like this:

<Grid Grid.Row="2" IsEnabled="{Binding ElementName=dgCustomers, Path=SelectedItem.Value}">
      <my:ProductsHistoryDetailView />
  </Grid>