Detecting WPF Validation Errors

Question

In WPF you can setup validation based on errors thrown in your Data Layer during Data Binding using the ExceptionValidationRule or DataErrorValidationRule.

Suppose you had a bunch of controls set up this way and you had a Save button. When the user clicks the Save button, you need to make sure there are no validation errors before proceeding with the save. If there are validation errors, you want to holler at them.

In WPF, how do you find out if any of your Data Bound controls have validation errors set?

Answer 1

This post was extremely helpful. Thanks to all who contributed. Here is a LINQ version that you will either love or hate.

private void CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    e.CanExecute = IsValid(sender as DependencyObject);
}

private bool IsValid(DependencyObject obj)
{
    // The dependency object is valid if it has no errors and all
    // of its children (that are dependency objects) are error-free.
    return !Validation.GetHasError(obj) &&
    LogicalTreeHelper.GetChildren(obj)
    .OfType<DependencyObject>()
    .All(IsValid);
}