C# WPF PropertyChanged event always null

Question

I have the following (abbreviated) xaml:

<TextBlock Text="{Binding Path=statusMsg, UpdateSourceTrigger=PropertyChanged}"/>

I have a singleton class:

public class StatusMessage : INotifyPropertyChanged
{   
    private static StatusMessage instance = new StatusMessage();

    private StatusMessage() { }

    public static StatusMessage GetInstance()
    {
        return instance;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string status)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(status));
        }
    }

    private string statusMessage;
    public string statusMsg
    {
        get
        {
            return statusMessage;
        }
        set
        {
            statusMessage = value;
            OnPropertyChanged("statusMsg");
        }
    }
}

And in my main window constructor:

StatusMessage testMessage = StatusMessage.GetInstance();
testMessage.statusMsg = "This is a test msg";

I cannot get the textblock to display the test message. When I monitor the code through debug, the PropertyChanged is always null. Any ideas?

Answer 1

your OnPropertyChanged string must exactly match the name of the property (it's case sensitive)

try changing OnPropertyChanged("StatusMsg"); to OnPropertyChanged("statusMsg");

HTH :)

edit: Also - just noticed that you're binding to StatusMsg (capital 'S'); so the control was not binding to the property, which is another reason why it wasn't updating!

cheers, IanR

Answer 2

Thanks Jerome! Once I set the DataContext it started working as it should! I added the following to the main window constructor for testing purposes:

 this.DataContext = testMessage;

Answer 3

It doesn't work for me, i always get null :S