Groupbox validating event
Therefore they can be accessed and styled in the 'standard' way, for example: See the excellent article Validation in WPF for details.
However, Binding Groups offer one further advantage, validation errors from the associated binding expressions are also placed in the Validation. Personally, I don't think there is one best approach - and this blog post is certainly not an attack on Sacha's article, which presents an elegant solution.
Rules associated with a Binding Group have access to both their associated binding expressions, and the source objects used by these bindings.
A Binding Group becomes associated with a collection of binding expressions if it shares the same Data Context.
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Unfortunately, the Error Provider control doesn't provide such functionality. Show("Validation failed.") End If End Sub internal Text Box email_textbox; internal Text Box city_textbox; internal Text Box address_textbox; internal Text Box phone_textbox; internal Text Box last Name_textbox; internal Text Box first Name_textbox; private Error Provider first Name_err Pro; private Error Provider last Name_err Pro; private Error Provider phone_err Pro; private Error Provider address_err Pro; private Error Provider city_err Pro; private Error Provider email_err Pro; internal Dictionary(6); errors. Add( email_err Pro ,email_textbox ); , or passing a more limited control collection.However, in the above example we have a pair of objects, therefore we cannot share a Data Context across all the elements in our XAML (this is not strictly true, we could construct a view model for this purpose, however I really want to illustrate one of the other features of Binding Groups).Binding Groups can also be explicitly associated with a Binding via its Binding Group Name property.In this instance, we are only interested in the converted value, hence the Validation Step property is set to Committed Value.The rule itself is very simple: We simply retrieve both Person instances, apply our rule raising an error if our condition is not met.