Basic Data Binding Concepts
Regardless of what element you are binding and the nature of your data source, each binding always follows the model illustrated by the following figure:
Basic data binding diagram
As illustrated by the above figure, data binding is essentially the bridge between your binding target and your binding source. The figure demonstrates the following fundamental WPF data binding concepts:
- Typically, each binding has these four components: a binding target object, a target property, a binding source, and a path to the value in the binding source to use. For example, if you want to bind the content of a TextBox to the Name property of an Employee object, your target object is the TextBox, the target property is the Text property, the value to use is Name, and the source object is the Employee object.
- The target property must be a dependency property. Most UIElement properties are dependency properties and most dependency properties, except read-only ones, support data binding by default. (Only DependencyObject types can define dependency properties and all UIElements derive from DependencyObject.)
- Although not specified in the figure, it should be noted that the binding source object is not restricted to being a custom CLR object. WPF data binding supports data in the form of CLR objects and XML. To provide some examples, your binding source may be a UIElement, any list object, a CLR object that is associated with ADO.NET data or Web Services, or an XmlNode that contains your XML data. For more information, see Binding Sources Overview.
As you read through other software development kit (SDK) topics, it is important to remember that when you are establishing a binding, you are binding a binding target to a binding source. For example, if you are displaying some underlying XML data in a ListBox using data binding, you are binding your ListBox to the XML data.
To establish a binding, you use the Binding object. The rest of this topic discusses many of the concepts associated with and some of the properties and usage of the Binding object.
Direction of the Data Flow
As mentioned previously and as indicated by the arrow in the figure above, the data flow of a binding can go from the binding target to the binding source (for example, the source value changes when a user edits the value of a TextBox) and/or from the binding source to the binding target (for example, your TextBox content gets updated with changes in the binding source) if the binding source provides the proper notifications.
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