WPF Databind Before Saving

Question

In my WPF application, I have a number of databound TextBoxes. The UpdateSourceTrigger for these bindings is LostFocus. The object is saved using t

Answer 1

Suppose you have a TextBox in a window, and a ToolBar with a Save button in it. Assume the TextBox’s Text property is bound to a property on a business object, and the binding’s UpdateSourceTrigger property is set to the default value of LostFocus, meaning that the bound value is pushed back to the business object property when the TextBox loses input focus. Also, assume that the ToolBar’s Save button has its Command property set to ApplicationCommands.Save command.

In that situation, if you edit the TextBox and click the Save button with the mouse, there is a problem. When clicking on a Button in a ToolBar, the TextBox does not lose focus. Since the TextBox’s LostFocus event does not fire, the Text property binding does not update the source property of the business object.

Obviously you should not validate and save an object if the most recently edited value in the UI has not yet been pushed into the object. This is the exact problem Karl had worked around, by writing code in his window that manually looked for a TextBox with focus and updated the source of the data binding. His solution worked fine, but it got me thinking about a generic solution that would also be useful outside of this particular scenario. Enter CommandGroup…

Taken from Josh Smith’s CodeProject article about CommandGroup