Data Binding in Code
At times, you may find that you need to bind the property of a control in the code behind. This is possible using the GetBindingExpression and SetBinding methods on the control.
To create a new binding and assign it to a control property, simply instantiate a Binding object (found in the System.Windows.Data namespace), assign the binding configuration to its properties as required, and apply the binding to the target control property using the control's SetBinding method. The SetBinding method requires you to pass it the Binding object and the dependency property identifier associated with the property to bind to on the target control, remembering that you can assign data bindings only to dependency properties.
For example, let's bind the Name property of a Product entity to the Text property of a TextBox control named NameTextBox:
Binding binding = new Binding("Name");
binding.Mode = BindingMode.TwoWay;
NameTextBox.SetBinding(TextBox.TextProperty, binding);
This example of creating a binding in code is simple, but of course, you can assign values to all the other binding properties that we have previously discussed, such as StringFormat, TargetNullValue, FallbackValue, and Source.
You can obtain the binding assigned to a control's property using the GetBindingExpression method on the control.
BindingExpression expr = NameTextBox.GetBindingExpression(TextBox.TextProperty);
As its name suggests, this method does not actually return a Binding object but returns a BindingExpression object instead. The BindingExpression class has two properties: ParentBinding and DataItem, in addition to the UpdateSource method discussed earlier. The ParentBinding property provides the Binding object assigned to the control property, and the DataItem property provides the object acting as the source for the binding.