WPF - Show command-line args in a label

Question

I have a wpf application that needs to be called with several command line arguments. How do I show them in the labels that I have put in the window just for that reason? I tried to implement data binding, but without success, - the variable is read and assigned correctly, but for some absurd reason is not shown on screen, in the label I want. Here is the code:

public partial class MainWindow : Window
{
    public Notification _notif = new Notification();
    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = new Notification();
    }

    protected override void OnClosed(EventArgs e)
    {
        base.OnClosed(e);
        App.Current.Shutdown();
    }
}

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e){
        if (e.Args.Length >= 4)
        {
            MainWindow mainWindow = new MainWindow();

            Label count_label = (Label)mainWindow.FindName("count");
            count_label.DataContext = mainWindow._notif;

            System.Diagnostics.Debug.WriteLine(mainWindow._notif.count + " - notif.count");
            // bind the Date to the UI
            count_label.SetBinding(Label.ContentProperty, new Binding("count")
            {
                Source = mainWindow._notif,
                Mode = BindingMode.TwoWay
            });
            //assigning values to the labels

            System.Diagnostics.Debug.WriteLine(count_label.Content + " - content of the label 'count'");
            mainWindow._notif.count = e.Args[0];
            System.Diagnostics.Debug.WriteLine(e.Args[0] + " is the argument n. 0");
            System.Diagnostics.Debug.WriteLine(mainWindow._notif.count + " - notif.count");


            System.Diagnostics.Debug.WriteLine(count_label.Content + "-------------------");

            System.Diagnostics.Debug.WriteLine(count_label.Content + " - content of the label 'count'");
            mainWindow._notif.count = "1234";
            System.Diagnostics.Debug.WriteLine(mainWindow._notif.count + " - notif.count");
            System.Diagnostics.Debug.WriteLine(count_label.Content + " - content of the label 'count'");

        }
    }
}

public class Notification : INotifyPropertyChanged
{
    private string _count;

    public string count {
        get {
            return _count;
        }

        set {
            _count = value;
            OnPropertyChanged("count");
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    #endregion
}

And here you can see a snippet from the xaml:

<Label x:Name="count" Content="{Binding count}" HorizontalAlignment="Center" Margin="0,10,486,0" VerticalAlignment="Top" RenderTransformOrigin="-2.895,-0.769" Height="80" Width="145" FontFamily="Arial" FontSize="64" HorizontalContentAlignment="Center"/>

Thank you anticipately.

Instance of MainWindow inside your App OnStartUp method is not the same as the StartupUri specified in App.xaml — Mikko Viitala, Sep 21 '15 at 16:11
To pass your args to the MainWindow you have to create a Property inside the MainWindow, for example a List property named CommandArgs, and after you create your MainWindow Object cycle the Args list and add its content to the CommandArgs List — Sabrina_cs, Sep 21 '15 at 16:22

hcp · Accepted Answer · 2015-09-21T18:15:45.043

The example illustrate how to display arguments in a label.

This is the entry point of the application:

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        var argumentsInfo = BuildArgumentsInfo(e.Args);
        var viewModel = new MainWindowViewModel(argumentsInfo);
        var window = new MainWindow(viewModel);
        window.Show();
    }

    private string BuildArgumentsInfo(string[] args)
    {
        return args.Any()
            ? args.Aggregate((arg1, arg2) => arg1 + " " + arg2)
            : "No arguments";
    }
}

This is the view model (a data context of the view):

public interface IMainWindowViewModel
{
    string Arguments { get; set; }
}

public class MainWindowViewModel : IMainWindowViewModel, INotifyPropertyChanged
{
    private string _arguments;

    public MainWindowViewModel(string argumentsInfo)
    {
        Arguments = argumentsInfo;
    }

    public string Arguments
    {
        get { return _arguments; }
        set
        {
            _arguments = value;
            RaisePropertyChanged("Arguments");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged = delegate {};

    private void RaisePropertyChanged(string propertyName)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

This is the view (code behind):

public partial class MainWindow : Window
{
    public MainWindow(IMainWindowViewModel viewModel)
    {
        InitializeComponent();
        DataContext = viewModel;
    }
}

And this is a label in the view (XAML):

<Label Content ="{Binding Arguments}"></Label>

Important! Your must delete StartupUri="MainWindow.xaml from App.xaml file because MainWindow is launched from a code behind.

WPF - Show command-line args in a label

1 Answers1