How to handle validation in Silverlight?

Question

How did you decide to handle data validation / control in Silverlight applications?

Answer 1

You can create exceptions to validate data.

To manage these two types of errors, you must complete 3 steps:

• Define an error handler either in the control or higher in the visibility hierarchy (for example, in a container, in this case a grid containing a text field)
• Set the value of NotifyOnValidationError and ValidateOnException to true. The latter tells the Binding Engine to raise a validation error event when an exception occurs. The first tells the Binding Engine to raise a BindingValidationError event when a validation error occurs.
• Create the event handler specified in step 1.

Taken from here .

Code example:

// page.xaml.cs private bool clean = true; private void LayoutRoot_BindingValidationError( object sender, ValidationErrorEventArgs e ) { if ( e.Action == ValidationErrorEventAction.Added ) { QuantityOnHand.Background = new SolidColorBrush( Colors.Red ); clean = false; } else if ( e.Action == ValidationErrorEventAction.Removed ) { QuantityOnHand.Background = new SolidColorBrush( Colors.White ); clean = true; } } // page.xaml <Grid x:Name="LayoutRoot" Background="White" BindingValidationError="LayoutRoot_BindingValidationError" > <TextBox x:Name="QuantityOnHand" Text="{Binding Mode=TwoWay, Path=QuantityOnHand, NotifyOnValidationError=true, ValidatesOnExceptions=true }" VerticalAlignment="Bottom" HorizontalAlignment="Left" Height="30" Width="90"red Grid.Row="4" Grid.Column="1" /> // book.cs public int QuantityOnHand { get { return quantityOnHand; } set { if ( value < 0 ) { throw new Exception( "Quantity on hand cannot be negative!" ); } quantityOnHand = value; NotifyPropertyChanged( "QuantityOnHand" ); } // end set } 

Answer 2

Didn't do this anymore, but some good starting points are here . I assume that they will come as part of a future release, but for now, we will probably have to roll using ASP.NET validators as a starting point.

Answer 3

If you are having trouble trying to implement this, it is not because your code is broken, because this function is broken in the DataGrid. Check out Jesse Liberty's article here .

Answer 4

At this point, a very simple verification control code is indicated:

http://silverlightvalidator.codeplex.com/SourceControl/changeset/view/20754#

Below are the conditions under which it works. 1. An indicator showing invalid values ​​takes the position of the control to check, so the controls should be tightly packed in a row and column so that they point to adjacent controls. 2. This does not work for validation in ChildWindow.

I had to modify the code to include childwindow conditions in the validatorbase class as follows:

Answer 5

 using System; using System.Net; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes; using Silverlight.Validators.Controls; namespace Silverlight.Validators { public enum ValidationType { Validator, OnDemand } public abstract class ValidatorBase : DependencyObject { protected ValidatorManager Manager { get; set; } public string ManagerName { get; set; } public ValidationType ValidationType { get; set; } public IIndicator Indicator { get; set; } public FrameworkElement ElementToValidate { get; set; } public bool IsRequired { get; set; } public bool IsValid { get; set; } public Brush InvalidBackground { get; set; } public Brush InvalidBorder { get; set; } public Thickness InvalidBorderThickness { get; set; } public string ErrorMessage { get; set; } private Brush OrigBackground = null; private Brush OrigBorder = null; private Thickness OrigBorderThickness = new Thickness(1); private object OrigTooltip = null; public ValidatorBase() { IsRequired = false; IsValid = true; ManagerName = ""; this.ValidationType = ValidationType.Validator; } public void Initialize(FrameworkElement element) { ElementToValidate = element; element.Loaded += new RoutedEventHandler(element_Loaded); } private bool loaded = false; public UserControl UserControl { get; set; } public ChildWindow ChildUserControl { get; set; } private void element_Loaded(object sender, RoutedEventArgs e) { if (!loaded) { this.UserControl = FindUserControl(ElementToValidate); //UserControl o = FindUserControl(ElementToValidate); this.ChildUserControl = FindChildUserControl(ElementToValidate); //MessageBox.Show(o.GetType().BaseType.ToString()); //no usercontrol. throw error? if ((this.UserControl == null) && (this.ChildUserControl==null)) return; if (this.UserControl != null) this.Manager = FindManager(this.UserControl, ManagerName); else if (this.ChildUserControl != null) this.Manager = FindManager(this.ChildUserControl, ManagerName); if (this.Manager == null) { System.Diagnostics.Debug.WriteLine(String.Format("No ValidatorManager found named '{0}'", ManagerName)); throw new Exception(String.Format("No ValidatorManager found named '{0}'", ManagerName)); } this.Manager.Register(ElementToValidate, this); if (ValidationType == ValidationType.Validator) { ActivateValidationRoutine(); } //Use the properties from the manager if they are not set at the control level if (this.InvalidBackground == null) { this.InvalidBackground = this.Manager.InvalidBackground; } if (this.InvalidBorder == null) { this.InvalidBorder = this.Manager.InvalidBorder; if (InvalidBorderThickness.Bottom == 0) { this.InvalidBorderThickness = this.Manager.InvalidBorderThickness; } } if (this.Indicator ==null) { Type x = this.Manager.Indicator.GetType(); this.Indicator = x.GetConstructor(System.Type.EmptyTypes).Invoke(null) as IIndicator; foreach (var param in x.GetProperties()) { var val = param.GetValue(this.Manager.Indicator, null); if (param.CanWrite && val!= null && val.GetType().IsPrimitive) { param.SetValue(this.Indicator, val, null); } } } loaded = true; } ElementToValidate.Loaded -= new RoutedEventHandler(element_Loaded); } public void SetManagerAndControl(ValidatorManager manager, FrameworkElement element) { this.Manager = manager; this.ElementToValidate = element; } public bool Validate(bool checkControl) { bool newIsValid; if (checkControl) { newIsValid= ValidateControl() && ValidateRequired(); } else { newIsValid = ValidateRequired(); } if (newIsValid && !IsValid) { ControlValid(); } if (!newIsValid && IsValid) { ControlNotValid(); } IsValid=newIsValid; return IsValid; } public virtual void ActivateValidationRoutine() { ElementToValidate.LostFocus += new RoutedEventHandler(ElementToValidate_LostFocus); ElementToValidate.KeyUp += new KeyEventHandler(ElementToValidate_KeyUp); } /// <summary> /// Find the nearest UserControl up the control tree for the FrameworkElement passed in /// </summary> /// <param name="element">Control to validate</param> protected static UserControl FindUserControl(FrameworkElement element) { if (element == null) { return null; } if (element.Parent != null) { //MessageBox.Show(element.Parent.GetType().BaseType.ToString()); if (element.Parent is UserControl) { return element.Parent as UserControl; } return FindUserControl(element.Parent as FrameworkElement); } return null; } protected static ChildWindow FindChildUserControl(FrameworkElement element) { if (element == null) { return null; } if (element.Parent != null) { //MessageBox.Show(element.Parent.GetType().BaseType.ToString()); if (element.Parent is ChildWindow) { return element.Parent as ChildWindow; } return FindChildUserControl(element.Parent as FrameworkElement); } return null; } protected virtual void ElementToValidate_KeyUp(object sender, RoutedEventArgs e) { Dispatcher.BeginInvoke(delegate() { Validate(false); }); } protected virtual void ElementToValidate_LostFocus(object sender, RoutedEventArgs e) { Dispatcher.BeginInvoke(delegate() { Validate(true); }); } protected abstract bool ValidateControl(); protected bool ValidateRequired() { if (IsRequired && ElementToValidate is TextBox) { TextBox box = ElementToValidate as TextBox; return !String.IsNullOrEmpty(box.Text); } return true; } protected void ControlNotValid() { GoToInvalidStyle(); } protected void ControlValid() { GoToValidStyle(); } protected virtual void GoToInvalidStyle() { if (!string.IsNullOrEmpty(this.ErrorMessage)) { object tooltip = ToolTipService.GetToolTip(ElementToValidate); if (tooltip != null) { OrigTooltip = tooltip; } //causing a onownermouseleave error currently... this.ElementToValidate.ClearValue(ToolTipService.ToolTipProperty); SetToolTip(this.ElementToValidate, this.ErrorMessage); } if (Indicator != null) { Indicator.ShowIndicator(this); } if (ElementToValidate is TextBox) { TextBox box = ElementToValidate as TextBox; if (InvalidBackground != null) { if (OrigBackground == null) { OrigBackground = box.Background; } box.Background = InvalidBackground; } if (InvalidBorder != null) { if (OrigBorder == null) { OrigBorder = box.BorderBrush; OrigBorderThickness = box.BorderThickness; } box.BorderBrush = InvalidBorder; if (InvalidBorderThickness != null) { box.BorderThickness = InvalidBorderThickness; } } } } protected virtual void GoToValidStyle() { if (!string.IsNullOrEmpty(this.ErrorMessage)) { this.ElementToValidate.ClearValue(ToolTipService.ToolTipProperty); if (this.OrigTooltip != null) { SetToolTip(this.ElementToValidate, this.OrigTooltip); } } if (Indicator != null) { Indicator.HideIndicator(); } if (ElementToValidate is TextBox) { TextBox box = ElementToValidate as TextBox; if (OrigBackground != null) { box.Background = OrigBackground; } if (OrigBorder != null) { box.BorderBrush = OrigBorder; if (OrigBorderThickness != null) { box.BorderThickness = OrigBorderThickness; } } } } protected void SetToolTip(FrameworkElement element, object tooltip) { Dispatcher.BeginInvoke(() => ToolTipService.SetToolTip(element, tooltip)); } private ValidatorManager FindManager(UserControl c, string groupName) { string defaultName = "_DefaultValidatorManager"; var mgr = this.UserControl.FindName(ManagerName); if (mgr == null) { mgr = this.UserControl.FindName(defaultName); } if (mgr == null) { mgr = new ValidatorManager() { Name = defaultName }; Panel g = c.FindName("LayoutRoot") as Panel; g.Children.Add(mgr as ValidatorManager); } return mgr as ValidatorManager; } private ValidatorManager FindManager(ChildWindow c, string groupName) { string defaultName = "_DefaultValidatorManager"; var mgr = this.ChildUserControl.FindName(ManagerName); if (mgr == null) { mgr = this.ChildUserControl.FindName(defaultName); } if (mgr == null) { mgr = new ValidatorManager() { Name = defaultName }; Panel g = c.FindName("LayoutRoot") as Panel; g.Children.Add(mgr as ValidatorManager); } return mgr as ValidatorManager; } } } 

Answer 6

You might want to check out PostSharp , which makes it very easy to bind your data model on the client side.