How DataMode is used

In this recipe let's understand the DataMode property of the Binding class. By default, the Data Mode property is OneWay. It has two other modes, OneTime and TwoWay . OneTime mode pulls the data only once from the source. OneWay mode only pulls the data from the source and updates it every time the source changes. TwoWay mode not only pulls the data from the source, but also pushes the changes back. These settings are not only used for data sources, they can also be tied to another element. Let's learn how we can use a TwoWay mode for the slider control to indicate the changes in a text block.

Getting ready

Create a new solution from the template Ch1_Recipe and name it Ch1_Recipe4_Mode.

How to do it...

1. Open the MainPage.xaml page and add a text block and a slider control to the existing page after the Notes text block. Here the slider control's value property is set to bind to text block control tbPriorityContent.

   <TextBlock x:Name ="tbPriorityContent" Text ="{Binding Priority}" Grid.Row="3" Grid.Column ="1" />
   
   <Slider x:Name ="slPriority" Width="300" Minimum="1" Maximum="10" Grid.Row="4" SmallChange="10" Grid.ColumnSpan ="2" Orientation="Horizontal" HorizontalAlignment="Left" Value="{Binding ElementName=tbPriorityContent, Path=Text,   Mode=TwoWay}" />
   

2. Open the DataClass.cs file and add another property called Priority to the DataClass, as follows:

   public class DataClass
   {
     public string Name { get; set; }
     public string Notes { get; set; }
     public int Priority { get; set; }
   }

3. Open the MainPage.xaml.cs file and add another line in the object initializer to set the Priority to 8. This is illustrated in the following code:

   public MainPage()
   {
     InitializeComponent();
     // Initialize our data class
     myData = new DataClass()
     {
       Name = "Name 1",
       Notes = "Note 1",
       Priority = 8
     };1
   
     // Set the DataContext of the grid to DataClass
     LayoutRoot.DataContext = myData;

4. Press F5 to run the app. As we set the priority to 8, the slider will move automatically based on the text block tbPriorityContent content. Also, try to move the slider position and you will see the text block value also changing.

   

How it works...

You noticed that when the slider changes its position the priority text block gets updated automatically. Because of the two-way mode setting the text block gets the data updated in the control's property as soon as it is changed. Similarly, when the text block is initialized with a value, the slider value is changed. This demonstrates how the controls can be refreshed with two-way mode.

There's more...

To learn more on the Data Bindings topic check this MSDN article:

http://msdn.microsoft.com/en-us/library/ms752347.aspx

See also

Check the recipes titled Element Binding and DataContext to learn more about these topics. Also, check the recipe Building a Simple App.