Implement Validation for WPF TextBoxes
There a 3 ways to implement validation:
- Validation Rule
- Implementation of INotifyDataErrorInfo
- Implementation of IDataErrorInfo
Validation rule example:
public class NumericValidationRule : ValidationRule{ public Type ValidationType { get; set; } public override ValidationResult Validate(object value, CultureInfo cultureInfo) { string strValue = Convert.ToString(value); if (string.IsNullOrEmpty(strValue)) return new ValidationResult(false, $"Value cannot be coverted to string."); bool canConvert = false; switch (ValidationType.Name) { case "Boolean": bool boolVal = false; canConvert = bool.TryParse(strValue, out boolVal); return canConvert ? new ValidationResult(true, null) : new ValidationResult(false, $"Input should be type of boolean"); case "Int32": int intVal = 0; canConvert = int.TryParse(strValue, out intVal); return canConvert ? new ValidationResult(true, null) : new ValidationResult(false, $"Input should be type of Int32"); case "Double": double doubleVal = 0; canConvert = double.TryParse(strValue, out doubleVal); return canConvert ? new ValidationResult(true, null) : new ValidationResult(false, $"Input should be type of Double"); case "Int64": long longVal = 0; canConvert = long.TryParse(strValue, out longVal); return canConvert ? new ValidationResult(true, null) : new ValidationResult(false, $"Input should be type of Int64"); default: throw new InvalidCastException($"{ValidationType.Name} is not supported"); } }}XAML:
Very important: don't forget to set ValidatesOnTargetUpdated="True" it won't work without this definition.
<TextBox x:Name="Int32Holder" IsReadOnly="{Binding IsChecked,ElementName=CheckBoxEditModeController,Converter={converters:BooleanInvertConverter}}" Style="{StaticResource ValidationAwareTextBoxStyle}" VerticalAlignment="Center"> <!--Text="{Binding Converter={cnv:TypeConverter}, ConverterParameter='Int32', Path=ValueToEdit.Value, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}"--> <TextBox.Text> <Binding Path="Name" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged" Converter="{cnv:TypeConverter}" ConverterParameter="Int32" ValidatesOnNotifyDataErrors="True" ValidatesOnDataErrors="True" NotifyOnValidationError="True"> <Binding.ValidationRules> <validationRules:NumericValidationRule ValidationType="{x:Type system:Int32}" ValidatesOnTargetUpdated="True" /> </Binding.ValidationRules> </Binding> </TextBox.Text> <!--NumericValidationRule--></TextBox>INotifyDataErrorInfo example:
public abstract class ViewModelBase : INotifyPropertyChanged, INotifyDataErrorInfo{ #region INotifyPropertyChanged public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged([CallerMemberName] string propertyName = null) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } ValidateAsync(); } #endregion public virtual void OnLoaded() { } #region INotifyDataErrorInfo private ConcurrentDictionary<string, List<string>> _errors = new ConcurrentDictionary<string, List<string>>(); public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged; public void OnErrorsChanged(string propertyName) { var handler = ErrorsChanged; if (handler != null) handler(this, new DataErrorsChangedEventArgs(propertyName)); } public IEnumerable GetErrors(string propertyName) { List<string> errorsForName; _errors.TryGetValue(propertyName, out errorsForName); return errorsForName; } public bool HasErrors { get { return _errors.Any(kv => kv.Value != null && kv.Value.Count > 0); } } public Task ValidateAsync() { return Task.Run(() => Validate()); } private object _lock = new object(); public void Validate() { lock (_lock) { var validationContext = new ValidationContext(this, null, null); var validationResults = new List<ValidationResult>(); Validator.TryValidateObject(this, validationContext, validationResults, true); foreach (var kv in _errors.ToList()) { if (validationResults.All(r => r.MemberNames.All(m => m != kv.Key))) { List<string> outLi; _errors.TryRemove(kv.Key, out outLi); OnErrorsChanged(kv.Key); } } var q = from r in validationResults from m in r.MemberNames group r by m into g select g; foreach (var prop in q) { var messages = prop.Select(r => r.ErrorMessage).ToList(); if (_errors.ContainsKey(prop.Key)) { List<string> outLi; _errors.TryRemove(prop.Key, out outLi); } _errors.TryAdd(prop.Key, messages); OnErrorsChanged(prop.Key); } } } #endregion}View Model Implementation:
public class MainFeedViewModel : BaseViewModel//, IDataErrorInfo{ private ObservableCollection<FeedItemViewModel> _feedItems; [XmlIgnore] public ObservableCollection<FeedItemViewModel> FeedItems { get { return _feedItems; } set { _feedItems = value; OnPropertyChanged("FeedItems"); } } [XmlIgnore] public ObservableCollection<FeedItemViewModel> FilteredFeedItems { get { if (SearchText == null) return _feedItems; return new ObservableCollection<FeedItemViewModel>(_feedItems.Where(x => x.Title.ToUpper().Contains(SearchText.ToUpper()))); } } private string _title; [Required] [StringLength(20)] //[CustomNameValidationRegularExpression(5, 20)] [CustomNameValidationAttribute(3, 20)] public string Title { get { return _title; } set { _title = value; OnPropertyChanged("Title"); } } private string _url; [Required] [StringLength(200)] [Url] //[CustomValidation(typeof(MainFeedViewModel), "UrlValidation")] /// <summary> /// Validation of URL should be with custom method like the one that implemented below, or with /// </summary> public string Url { get { return _url; } set { _url = value; OnPropertyChanged("Url"); } } public MainFeedViewModel(string url, string title) { Title = title; Url = url; } /// <summary> /// /// </summary> public MainFeedViewModel() { } public MainFeedViewModel(ObservableCollection<FeedItemViewModel> feeds) { _feedItems = feeds; } private string _searchText; [XmlIgnore] public string SearchText { get { return _searchText; } set { _searchText = value; OnPropertyChanged("SearchText"); OnPropertyChanged("FilteredFeedItems"); } } #region Data validation local /// <summary> /// Custom URL validation method /// </summary> /// <param name="obj"></param> /// <param name="context"></param> /// <returns></returns> public static ValidationResult UrlValidation(object obj, ValidationContext context) { var vm = (MainFeedViewModel)context.ObjectInstance; if (!Uri.IsWellFormedUriString(vm.Url, UriKind.Absolute)) { return new ValidationResult("URL should be in valid format", new List<string> { "Url" }); } return ValidationResult.Success; } #endregion}XAML:
<UserControl x:Class="RssReaderTool.Views.AddNewFeedDialogView" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300"> <FrameworkElement.Resources> <Style TargetType="{x:Type TextBox}"> <Setter Property="Validation.ErrorTemplate"> <Setter.Value> <ControlTemplate x:Name="TextErrorTemplate"> <DockPanel LastChildFill="True"> <AdornedElementPlaceholder> <Border BorderBrush="Red" BorderThickness="2" /> </AdornedElementPlaceholder> <TextBlock FontSize="20" Foreground="Red">*?*</TextBlock> </DockPanel> </ControlTemplate> </Setter.Value> </Setter> <Style.Triggers> <Trigger Property="Validation.HasError" Value="True"> <Setter Property="ToolTip" Value="{Binding RelativeSource= {x:Static RelativeSource.Self}, Path=(Validation.Errors)[0].ErrorContent}"></Setter> </Trigger> </Style.Triggers> </Style> <!--<Style TargetType="{x:Type TextBox}"> <Style.Triggers> <Trigger Property="Validation.HasError" Value="true"> <Setter Property="ToolTip" Value="{Binding RelativeSource={x:Static RelativeSource.Self}, Path=(Validation.Errors)[0].ErrorContent}" /> </Trigger> </Style.Triggers> </Style>--> </FrameworkElement.Resources> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="5" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> <RowDefinition Height="5" /> <RowDefinition Height="Auto" /> <RowDefinition Height="5" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <TextBlock Text="Feed Name" ToolTip="Display" /> <TextBox Text="{Binding MainFeedViewModel.Title,UpdateSourceTrigger=PropertyChanged,ValidatesOnNotifyDataErrors=True,ValidatesOnDataErrors=True}" Grid.Column="2" /> <TextBlock Text="Feed Url" Grid.Row="2" /> <TextBox Text="{Binding MainFeedViewModel.Url,UpdateSourceTrigger=PropertyChanged,ValidatesOnNotifyDataErrors=True,ValidatesOnDataErrors=True}" Grid.Column="2" Grid.Row="2" /> </Grid></UserControl>IDataErrorInfo:
View Model:
public class OperationViewModel : ViewModelBase, IDataErrorInfo{ private const int ConstCodeMinValue = 1; private readonly IEventAggregator _eventAggregator; private OperationInfoDefinition _operation; private readonly IEntityFilterer _contextFilterer; private OperationDescriptionViewModel _description; public long Code { get { return _operation.Code; } set { if (SetProperty(value, _operation.Code, o => _operation.Code = o)) { UpdateDescription(); } } } public string Description { get { return _operation.Description; } set { if (SetProperty(value, _operation.Description, o => _operation.Description = o)) { UpdateDescription(); } } } public string FriendlyName { get { return _operation.FriendlyName; } set { if (SetProperty(value, _operation.FriendlyName, o => _operation.FriendlyName = o)) { UpdateDescription(); } } } public int Timeout { get { return _operation.Timeout; } set { if (SetProperty(value, _operation.Timeout, o => _operation.Timeout = o)) { UpdateDescription(); } } } public string Category { get { return _operation.Category; } set { if (SetProperty(value, _operation.Category, o => _operation.Category = o)) { UpdateDescription(); } } } public bool IsManual { get { return _operation.IsManual; } set { if (SetProperty(value, _operation.IsManual, o => _operation.IsManual = o)) { UpdateDescription(); } } } void UpdateDescription() { //some code } #region Validation #region IDataErrorInfo public ValidationResult Validate() { return ValidationService.Instance.ValidateNumber(Code, ConstCodeMinValue, long.MaxValue); } public string this[string columnName] { get { var validation = ValidationService.Instance.ValidateNumber(Code, ConstCodeMinValue, long.MaxValue); return validation.IsValid ? null : validation.ErrorContent.ToString(); } } public string Error { get { var result = Validate(); return result.IsValid ? null : result.ErrorContent.ToString(); } } #endregion #endregion}XAML:
<controls:NewDefinitionControl x:Class="DiagnosticsDashboard.EntityData.Operations.Views.NewOperationView" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:views="clr-namespace:DiagnosticsDashboard.EntityData.Operations.Views" xmlns:controls="clr-namespace:DiagnosticsDashboard.Core.Controls;assembly=DiagnosticsDashboard.Core" xmlns:c="clr-namespace:DiagnosticsDashboard.Core.Validation;assembly=DiagnosticsDashboard.Core" mc:Ignorable="d"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="*" /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="40" /> <RowDefinition Height="40" /> <RowDefinition Height="40" /> <RowDefinition Height="40" /> <RowDefinition Height="40" /> <RowDefinition Height="40" /> <RowDefinition Height="*" /> <RowDefinition Height="*" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <Label Grid.Column="0" Grid.Row="0" Margin="5">Code:</Label> <Label Grid.Column="0" Grid.Row="1" Margin="5">Description:</Label> <Label Grid.Column="0" Grid.Row="2" Margin="5">Category:</Label> <Label Grid.Column="0" Grid.Row="3" Margin="5">Friendly Name:</Label> <Label Grid.Column="0" Grid.Row="4" Margin="5">Timeout:</Label> <Label Grid.Column="0" Grid.Row="5" Margin="5">Is Manual:</Label> <TextBox Grid.Column="1" Text="{Binding Code,UpdateSourceTrigger=PropertyChanged,ValidatesOnDataErrors=True}" Grid.Row="0" Margin="5"/> <TextBox Grid.Column="1" Grid.Row="1" Margin="5" Text="{Binding Description}" /> <TextBox Grid.Column="1" Grid.Row="2" Margin="5" Text="{Binding Category}" /> <TextBox Grid.Column="1" Grid.Row="3" Margin="5" Text="{Binding FriendlyName}" /> <TextBox Grid.Column="1" Grid.Row="4" Margin="5" Text="{Binding Timeout}" /> <CheckBox Grid.Column="1" Grid.Row="5" Margin="5" IsChecked="{Binding IsManual}" VerticalAlignment="Center" /> </Grid></controls:NewDefinitionControl>
You can additionally implement IDataErrorInfo as follows in the view model. If you implement IDataErrorInfo, you can do the validation in that instead of the setter of a particular property, then whenever there is a error, return an error message so that the text box which has the error gets a red box around it, indicating an error.
class ViewModel : INotifyPropertyChanged, IDataErrorInfo{ private string m_Name = "Type Here"; public ViewModel() { } public string Name { get { return m_Name; } set { if (m_Name != value) { m_Name = value; OnPropertyChanged("Name"); } } } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } public string Error { get { return "...."; } } /// <summary> /// Will be called for each and every property when ever its value is changed /// </summary> /// <param name="columnName">Name of the property whose value is changed</param> /// <returns></returns> public string this[string columnName] { get { return Validate(columnName); } } private string Validate(string propertyName) { // Return error message if there is error on else return empty or null string string validationMessage = string.Empty; switch (propertyName) { case "Name": // property name // TODO: Check validiation condition validationMessage = "Error"; break; } return validationMessage; }}And you have to set ValidatesOnDataErrors=True in the XAML in order to invoke the methods of IDataErrorInfo as follows:
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
To get it done only with XAML you need to add Validation Rules for individual properties. But i would recommend you to go with code behind approach. In your code, define your specifications in properties setters and throw exceptions when ever it doesn't compliance to your specifications. And use error template to display your errors to user in UI. Your XAML will look like this
<Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"><Window.Resources> <Style x:Key="CustomTextBoxTextStyle" TargetType="TextBox"> <Setter Property="Foreground" Value="Green" /> <Setter Property="MaxLength" Value="40" /> <Setter Property="Width" Value="392" /> <Style.Triggers> <Trigger Property="Validation.HasError" Value="True"> <Trigger.Setters> <Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=(Validation.Errors)[0].ErrorContent}"/> <Setter Property="Background" Value="Red"/> </Trigger.Setters> </Trigger> </Style.Triggers> </Style></Window.Resources><Grid> <TextBox Name="tb2" Height="30" Width="400" Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=True}" Style="{StaticResource CustomTextBoxTextStyle}"/></Grid>Code Behind:
public partial class MainWindow : Window{ private ExampleViewModel m_ViewModel; public MainWindow() { InitializeComponent(); m_ViewModel = new ExampleViewModel(); DataContext = m_ViewModel; }}public class ExampleViewModel : INotifyPropertyChanged{ private string m_Name = "Type Here"; public ExampleViewModel() { } public string Name { get { return m_Name; } set { if (String.IsNullOrEmpty(value)) { throw new Exception("Name can not be empty."); } if (value.Length > 12) { throw new Exception("name can not be longer than 12 charectors"); } if (m_Name != value) { m_Name = value; OnPropertyChanged("Name"); } } } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } }}