In my current project I'm having the pleasure of working with the Silverlight RadScheduler control.  While you may read and feel it is a very bloated control, I argue otherwise, it is highly extensible for such a complex control.  I really think the Telerik guys did a very good job.

My particular scenario is interesting.  I need to:

1. Extend the appointment dialog to support addresses
2. The addresses aren't always required (so I can't just use RequiredAttribute)
3. When fields are required, I'd like the validation to kick off and prevent me from saving that appointment

Here we go:

Updating the RadScheduler template:

This is pretty simple - find the EditAppointmentTemplate

  <ControlTemplate x:Key="EditAppointmentTemplate" TargetType="telerik:AppointmentDialogWindow">

1. Customize the control template, we added additional fields
2. NotifyOnValidationError and ValidatesOnException are important.

..snip

          <input:ValidationSummary x:Name="ValidationSummary" />

          <TextBlock Text="Suburb" Style="{StaticResource FormElementTextBlockStyle}"/>
          <TextBox Text="{Binding Suburb, Mode=TwoWay, NotifyOnValidationError=True, 
ValidatesOnExceptions=True}"  />

Extend the Appointment class:

1. Create a ValidationEnabled property - sometimes you need to "not validate"
2. Create a ValidateProperty method - this takes a property name and triggers all validate attributes on that property - Validator.ValidateProperty is the method that will trigger all kinds of fun validation exceptions for us.
3. Set the appropriate validation attributes on the property e.g. Suburb - I'm using a custom validation property that I've created based on the RequiredAttribute
4. In the setter, call ValidateProperty.

    public class JobAppointment : Appointment
    {
        private string _suburb;

        public ObservableCollection<ValidationError> Errors { get; set; }

        public bool ValidationEnabled
        {
            get;
            set;
        }

        private void ValidateProperty(string propertyName, object value)
        {
            if (ValidationEnabled)
            {
                var context = new ValidationContext(this, null, null);
                context.MemberName = propertyName;

                Validator.ValidateProperty(value, context);
            }
        }

        [ValidationRequired]
        public string Suburb
        {
            get
            {
                return _suburb;
            }
            set
            {
                ValidateProperty("Suburb", value);

                if (_suburb != value)
                {
                    _suburb = value;
                    OnPropertyChanged("Suburb");
                }
            }
        }

Add our own Validation attributes

1. This Required attribute checks against our settings to see if "Suburb" happens to be a required field.  If not, then skip the validation and just return success.

 public class ValidationRequiredAttribute : RequiredAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            if (SettingsLifeTimeService.Current != null )
            {
                if (SettingsLifeTimeService.Current.RequiredFields.Contains(validationContext.MemberName))
                {
                    // RequiredAttribute validation
                    return base.IsValid(value, validationContext);
                }
            }
            return ValidationResult.Success;
        }
    }

 

Stop validation on Scheduler's Appointment_Saving event

1. In the AppointmentSaving event, grab all the children framework elements from the appointment dialog window
2. Find their binding expression (e.g., for TextBox I want the binding expression for Textbox.Text)
3. If exists, I want it to push the values back into the datasource (our customized Appointment class) - this triggers the property setter (which triggers our ValidateProperty, which triggers the custom Required attribute)
4. Finally, check the validation summary to see if we have any binding errors, if we do, cancel the save.

void _scheduler_AppointmentSaving(object sender, AppointmentSavingEventArgs e)
        {
            JobAppointment jobApp = e.Appointment as JobAppointment;
            AppointmentDialogWindow window = e.OriginalSource as AppointmentDialogWindow;
            var children = window.ChildrenOfType<FrameworkElement>();

            if (children != null)
            {
                foreach (var element in children)
                {
                    BindingExpression binding = null;
                    if (element is TextBox)
                    {
                        binding = element.GetBindingExpression(TextBox.TextProperty);
                    }

                    if (binding != null)
                    {
                        // force control to update databound VM.  This triggers the validation.
                        binding.UpdateSource();
                    }
                }
            }

            ValidationSummary summary = window.FindChildByType<ValidationSummary>();

            if (summary != null)
            {
                if (summary.HasErrors)
                {
                    e.Cancel = true;
                    return;
                }
            }
        }

Finished!