The Binding class is the high-level class for the declaration of a binding. The BindingExpression class is the underlying object that maintains the connection between the binding source and the binding target. A Binding contains all the information that can be shared across several BindingExpression objects. A BindingExpression is an instance expression that cannot be shared and that contains all the instance information about the Binding.

For example, consider the following, where myDataObject is an instance of the MyData class, myBinding is the source Binding object, and MyData class is a defined class that contains a string property named MyDataProperty. This example binds the text content of mytext, which is an instance of TextBlock, to MyDataProperty.

Dim data1 As New MyData(DateTime.Now)
Dim binding1 As New Binding("MyDataProperty")
binding1.Source = data1
Me.myText.SetBinding(TextBlock.TextProperty, binding1)

//make a new source
  MyData myDataObject = new MyData(DateTime.Now);      
  Binding myBinding = new Binding("MyDataProperty");
  myBinding.Source = myDataObject;
  myText.SetBinding(TextBlock.TextProperty, myBinding);

You can use the same myBinding object to create other bindings. For example, you might use the myBinding object to bind the text content of a check box to MyDataProperty. In that scenario, there will be two instances of BindingExpression that share the myBinding object.

You can obtain a BindingExpression object by using the GetBindingExpression method or the GetBindingExpression method on a data-bound object.

This example shows how to obtain the binding object from a data-bound target property.

You can do the following to get the Binding object:

// textBox3 is an instance of a TextBox
// the TextProperty is the data-bound dependency property
Binding myBinding = BindingOperations.GetBinding(textBox3, TextBox.TextProperty);

Note:
You must specify the dependency property for the binding you want because it is possible that more than one property of the target object is using data binding.

Alternatively, you can get the BindingExpression and then get the value of the ParentBinding property.

For the complete example see Binding Validation Sample.

Note:
If your binding is a MultiBinding, use BindingOperations.GetMultiBinding. If it is a PriorityBinding, use BindingOperations.GetPriorityBinding. If you are uncertain whether the target property is bound using a Binding, a MultiBinding, or a PriorityBinding, you can use BindingOperations.GetBindingBase.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

.NET Framework

Reference

Other Resources