Binding the text property of the text block in a StatusBar from different pages

Question

I have a WPF application which has a MainWindow which is divided into 2 frames one for the left navigation menu and the other for the pages (like addFirm page , addlocation page etc). Now i want a status bar on the main window which must display messages which are raised in the pages. Something like this

<DockPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" LastChildFill="True"  >
    <StackPanel DockPanel.Dock="Top" Style="{DynamicResource SMMainStackPanel}" >
        <Border Style="{DynamicResource SMBorder}"  >
          <Label Content="System" FontSize="18" HorizontalContentAlignment="Center" />
        </Border>
    </StackPanel>
    <StackPanel DockPanel.Dock="Left" Style="{DynamicResource SMMainStackPanel}">
        <Border VerticalAlignment="Stretch" Style="{DynamicResource SMBorder}"  >
            <Frame Name="frame1" Source="Menu.xaml" Style="{DynamicResource SMMainFrame}" />
        </Border>
    </StackPanel>
    <StackPanel Style="{DynamicResource SMMainStackPanel}" >
       <Border Style="{DynamicResource SMBorder}" >                
            <Frame Name="frame2" Style="{DynamicResource SMMainFrame}"/>
        </Border>
        <DockPanel  VerticalAlignment="Stretch" HorizontalAlignment="Stretch" DockPanel.Dock="Bottom">
                   <StatusBar>
                    <StatusBar.ItemsPanel>
                        <ItemsPanelTemplate>
                            <Grid>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*"/>
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="4*"/>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="*"/>
                                </Grid.ColumnDefinitions>
                            </Grid>
                        </ItemsPanelTemplate>
                    </StatusBar.ItemsPanel>
                    <StatusBarItem>
                        <TextBlock>Ready</TextBlock>
                    </StatusBarItem>
                    <StatusBarItem Grid.Column="1">
                        <ProgressBar Value="30" Width="80" Height="18"/>
                    </StatusBarItem>
                    <StatusBarItem Grid.Column="2">
                    <TextBlock Text= "ABC" />
                    </StatusBarItem>
                    <StatusBarItem Grid.Column="3">
            <TextBlock Text="{Binding Source={x:Static sys:DateTime.Now}}"/>
                    </StatusBarItem>
                </StatusBar>
        </DockPanel>
    </StackPanel>
</DockPanel>

Now i want to populate the StatusBarItem from the message property of the below class instead of the static text "ABC". PS: The obejct of this class is created on the indivisual pages and not on the mainwindow

public class StatusHelper : INotifyPropertyChanged 
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _message;

    private void OnPropertyChanged(String property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }

    public string Message
    {
        get
        {
            return _message;
        }
        set
        {
            _message = value;
            OnPropertyChanged("Message");
        }
    }

}

I create the object of this class on the indivisual pages and then when an operation is completed then how i set the message property of this class.

The only link which i am missing is that how do i get the instance of this class which is set on a page (say suppose on addlocation) on the mainwindow.xaml. Also how do i bind this instance on the text property of the text area.

Answer 1

I got the answer to this question. What i did was to pass on the instance of the main page to a common helper class(which is static) in a static variable . Now Create a property on the main page which would return the instance of the status bar (sbMain). Call the status helper class from the master forms and call the update method on it.

Add property SmStatusBar to the MainWindow also passthe instance to the main Window to a class while the initilization of the main page as below

    public SmStatusBar StatusBar 
    {
        get { return this.sbMain; }
    }

    public MainWindow()
    {
        InitializeComponent();
        CommonHelper.SmMainWindow = this;
    }

Add a static property on the Common Helper class

    public static MainWindow MainWindow { get; set; }

Now Create a class StatusHelper

public static class StatusHelper
{
    private static SmStatusBar _statusBar;

    static StatusHelper()
    {
        _statusBar = CommonHelper.SmMainWindow.StatusBar;
    }

     public static bool UpdateStatus(string text)
     {
         _statusBar.UpdateStatusText(text);
         return true;
     }

}

Answer 2

If your StatusHelper object is the DataContext of the panel you've shown above, then setting up the binding in XAML is easy:

<TextBlock Text="{Binding Message}" />

If, for example, that panel has a PageViewModel object as its DataContext, which contains a StatusHelper property named 'Status', then you can bind to it as following:

<TextBlock Text="{Binding Status.Message}" />

The exact answer depends on how you've set up your view-model / data-context hierarchy.

Answer 3

If you don't already have one, add a base view model class to your application. Add a class that implements the Singleton Pattern to your application so that there can only be one instance of it. Add a reference to that class to your base view model, ensuring you only access it using the Instance property:

public StateManager StateManager
{
    get { return stateManager.Instance; }
}

Now every view model in your application has access to the properties from this class, so therefore you can data bind to them from every view:

<TextBlock Text= "{Binding StateManager.YourPropertyName}" />