Question

My application’s main component is a tab control which holds N number of views and those views’ datacontext is a separate ViewModel object. I have a statusbar at the bottom of the app and it contains a few textboxes. I want one of the textboxes to reflect a timestamp for the currently selected tab. The timestamp is a property of the ViewModel object that’s set as the view’s datacontext.

I’m a WPF newb and not really sure how to bind that property to the status bar.

Answer 1

Make sure your ViewModel implements INotifyPropertyChanged.

For example…

/// <summary>
/// Sample ViewModel.
/// </summary>
public class ViewModel : INotifyPropertyChanged
{
    #region Public Properties

    /// <summary>
    /// Timestamp property
    /// </summary>
    public DateTime Timestamp
    {
        get
        {
            return this._Timestamp;
        }
        set
        {
            if (value != this._Timestamp)
            {
                this._Timestamp = value;

                // NOTE: This is where the ProperyChanged event will get raised
                //       which will result in the UI automatically refreshing itself.
                OnPropertyChanged("Timestamp");
            }
        }
    }

    #endregion


    #region INotifyPropertyChanged Members

    /// <summary>
    /// Event
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    /// <summary>
    /// Raise the PropertyChanged event.
    /// </summary>
    protected void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    #endregion


    #region Private Fields

    private DateTime _Timestamp;

    #endregion
}