CODEWITHSUNDEEP
c#wpfmvvmprism
Rohit
Rohit

Reputation: 10236

How to perform command in WPF

I am using MVVM prism and my code is as follows

     <ListBox x:Name="myListBox"  Grid.Row="0"
         ItemsSource="{Binding Path=_mySOurce}" 
         ScrollViewer.VerticalScrollBarVisibility="Auto" 
         SelectionChanged="myListBox_SelectionChanged">
    </ListBox>
    <Button Grid.Row="1" x:Name="btnSelect" 
     Command="{Binding Path=SaveCommand}" Content="Select" Margin="396,0,10,0"></Button>

and in my code i have 

 public ICommand SaveCommand { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        this.SaveCommand = new DelegateCommand<object>(this.OnSaveClick, this.CanSaveExecute);       
    }

    private void myListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {

    }

    private void OnSaveClick(object arg)
    {

        MessageBox.Show("Performed Click");
    }
    private bool CanSaveExecute(object arg)
    {
        if (myListBox.SelectedIndex > 0)
            return true;

        else return false;
    }

I am not able to fire it at selection changed event.

What am I missing ?

Upvotes: 0

Views: 132

Answers (1)

Sheridan
Sheridan

Reputation: 69959

If you're handling a UI event in your view model, then you're not using MVVM at all! Handling UI events in the view model completely breaks the separation of concerns that MVVM provides.

However, the short answer is this:

private void myListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (SaveCommand.CanExecute(null)) SaveCommand.Execute(null);
}

A far better solution is to add another property to data bind to the ListBox.SelectedItem property:

<ListBox x:Name="myListBox"  Grid.Row="0" SelectedItem="{Binding CurrentItem}"
    ItemsSource="{Binding Path=_mySOurce}" 
    ScrollViewer.VerticalScrollBarVisibility="Auto" 
    SelectionChanged="myListBox_SelectionChanged" />

Then the setter for that CurrentItem property will be called whenever the SelectionChanged event would be called:

public YourDataType CurrentItem
{
    get { return currentItem; }
    set
    {
        currentItem = value;
        NotifyPropertyChanged("CurrentItem");
        if (SaveCommand.CanExecute(null)) SaveCommand.Execute(null);
    }
}

Upvotes: 1

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