Wpf – Force validation on bound controls in WPF

business-objectsvalidationwpf

I have a WPF dialog with a couple of textboxes on it.
Textboxes are bound to my business object and have WPF validation rules attached.

The problem is that user can perfectly click 'OK' button and close the dialog, without actually entering the data into textboxes. Validation rules never fire, since user didn't even attempt entering the information into textboxes.

Is it possible to force validation checks and determine if some validation rules are broken?

I would be able to do it when user tries to close the dialog and prohibit him from doing it if any validation rules are broken.

Thank you.

Best Answer

In 3.5SP1 / 3.0SP2, they also added a new property to the ValidationRule base, namely, ValidatesOnTargetUpdated="True". This will call the validation as soon as the source object is bound, rather than only when the target control is updated. That may not be exactly what you want, but it's not bad to see initially all the stuff you need to fix.

Works something like this:

<TextBox.Text>
    <Binding Path="Amount" StringFormat="C">
        <Binding.ValidationRules>
            <validation:RequiredValidationRule 
                ErrorMessage="The pledge amount is required." 
                ValidatesOnTargetUpdated="True"  />
            <validation:IsNumericValidationRule 
                ErrorMessage="The pledge amount must be numeric." 
                ValidationStep="ConvertedProposedValue" 
                ValidatesOnTargetUpdated="True"  />
        </Binding.ValidationRules>
    </Binding>
</TextBox.Text>

Related Solutions

Wpf – Detecting WPF Validation Errors

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);
}

Wpf – forcing Validation; WPF, DataGrid, ObservableCollection

For your bindings, set the UpdateSourceTrigger to property changed, and then put your validation rules inside that. The default update source trigger is Lost Focus.

  <Binding Path="Name" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <ExceptionValidationRule />
            </Binding.ValidationRules>
        </Binding>

Also, for another good solution, have a look here

http://www.codeproject.com/KB/WPF/wpfvalidation.aspx

Paul builds a custom error provider, like

You can call the Validate() method on the ErrorProvider to force validation, and check if the controls are valid

Best Answer

Related Solutions

Wpf – Detecting WPF Validation Errors

Wpf – forcing Validation; WPF, DataGrid, ObservableCollection

Related Topic