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.Row
