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title, ms.date, helpviewer_keywords, ms.assetid
| title | ms.date | helpviewer_keywords | ms.assetid | |||
|---|---|---|---|---|---|---|
| How to: Specify the Direction of the Binding | 03/30/2017 |
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37334478-028b-4514-86c9-1420709f4818 |
How to: Specify the direction of the binding
This example shows how to specify whether the binding updates only the binding target (target) property, the binding source (source) property, or both the target property and the source property.
Example
You use the xref:System.Windows.Data.Binding.Mode%2A?displayProperty=nameWithType property to specify the direction of the binding. The following are the available options for binding updates:
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xref:System.Windows.Data.BindingMode.TwoWay?displayProperty=nameWithType updates the target property or the property whenever either the target property or the source property changes.
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xref:System.Windows.Data.BindingMode.OneWay?displayProperty=nameWithType updates the target property only when the source property changes.
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xref:System.Windows.Data.BindingMode.OneTime?displayProperty=nameWithType updates the target property only when the application starts or when the xref:System.Windows.FrameworkElement.DataContext%2A undergoes a change.
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xref:System.Windows.Data.BindingMode.OneWayToSource?displayProperty=nameWithType updates the source property when the target property changes.
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xref:System.Windows.Data.BindingMode.Default?displayProperty=nameWithType causes the default xref:System.Windows.Data.Binding.Mode%2A value of target property to be used.
For more information, see the xref:System.Windows.Data.BindingMode enumeration.
The following example shows how to set the xref:System.Windows.Data.Binding.Mode%2A property.
[!code-xamlDirectionalBinding#4]
To detect source changes (applicable to xref:System.Windows.Data.BindingMode.OneWay and xref:System.Windows.Data.BindingMode.TwoWay bindings), the source must implement a suitable property change notification mechanism such as xref:System.ComponentModel.INotifyPropertyChanged. See Implement Property Change Notification for an example of an xref:System.ComponentModel.INotifyPropertyChanged implementation.
For xref:System.Windows.Data.BindingMode.TwoWay or xref:System.Windows.Data.BindingMode.OneWayToSource bindings, you can control the timing of the source updates by setting the xref:System.Windows.Data.Binding.UpdateSourceTrigger%2A property. See xref:System.Windows.Data.Binding.UpdateSourceTrigger%2A for more information.