Update ValidationSummary after UpdateSource

I'm forcing an update of every textBox in a silverlight page:

this.txtName.GetBindingExpression(TextBox.TextProperty).UpdateSource();

Everything works fine (the textbox shows its error, etc...) but ValidationSummary is not refreshed...

Any idea??

Edit:

After some tests I've realized it was because ValidationSummary wasn't loaded yet. I'll start a new question to ask this...

I just had to call the UpdateSource on Loaded page event.

NotifyOnValidationError = “True”?