I need to pass a bind value to my validation rule. This is the XAML code:
<Label Grid.Column="11" Content="Default" Style="{StaticResource labelStyle2}" x:Name="txtTipo" />
<TextBox Grid.Column="12" Style="{StaticResource txtDataStyle1}" Width="100" TextChanged="Data_TextChanged">
<Binding Path="ConfigObject.Edit.Default" UpdateSourceTrigger="Default">
<Binding.ValidationRules>
<local:GenericValidationRule>
<local:GenericValidationRule.Wrapper>
<local:Wrapper TipoInterno="{Binding ElementName=txtTipo, Path=Content}"/>
</local:GenericValidationRule.Wrapper>
</local:GenericValidationRule>
</Binding.ValidationRules>
</Binding>
</TextBox>
Codebehind:
public class GenericValidationRule : ValidationRule
{
public Wrapper Wrapper { get; set; }
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
var xx = Wrapper.TipoInternoProperty; //TEST
return new ValidationResult(is_valid, error_context);
}
}
public class Wrapper : DependencyObject
{
public static readonly DependencyProperty TipoInternoProperty = DependencyProperty.Register("TipoInterno", typeof(string), typeof(Wrapper), new PropertyMetadata(string.Empty));
public string TipoInterno
{
get { return (string)GetValue(TipoInternoProperty); }
set { SetValue(TipoInternoProperty, value); }
}
}
Basically I cannot get the required value into my TinoInterno property. If I hardcode a value such:
<local:Wrapper TipoInterno="TEST" />
the property is correctly valorized. In the first case I need to pass the property Content of control with elementName txtTipo.
What's wrong?
You should get the value of the TipoInterno of the Wrapper instance in the ValidationRule:
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
string s = Wrapper.TipoInterno;
return ...;
}
You could then bind using an x:Reference:
<local:Wrapper TipoInterno="{Binding Path=Content, Source={x:Reference txtTipo}}"/>
Related
In my WPF MVVM app I have a TextBox which has bound a validation rule.
In validation rule class I have below property:
public bool CanBeValidated { get; set; } = false;
Then in the view my TextBox has below validation rule bound (I only put the relevant part):
<TextBox.Text>
<Binding Path="myPath"
UpdateSourceTrigger="PropertyChanged"
ValidatesOnDataErrors="True">
<Binding.ValidationRules>
<vRules:RootPathValidationRule
ValidatesOnTargetUpdated="True"
CanBeValidated="{Binding Path=ValidationEnabled}"/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
In my view model the property is defined as below:
public bool ValidationEnabled
{
get { return _isValidationEnabled; }
set { this._isValidationEnabled = value; OnPropertyChanged(); }
}
So I receive below compilation error:
A 'Binding' cannot be set on the 'CanBeValidated' property of type
'MyPathValidatorRule'. A 'Binding' can only be set on a
DependencyProperty of a DependencyObject.
For first time when TextBox is loaded I want to avoid validation rule to fire until user edits it and avoid throwing a validation error since TextBox is empty.
Once user edits the TextBox, I would like to enable validation rule by performing a simple this.ValidationEnabled = true from view model.
How can I achieve this without using dependency properties? Is it possible?
You could create a wrapper class that derives from DependencyObject and exposes a dependency property. Then you add a CLR property to the ValidationRule class that returns an instance of this wrapper type:
public class RootPathValidationRule : ValidationRule
{
public Wrapper Wrapper { get; set; }
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
bool canBeValidated = Wrapper?.CanBeValidated == true;
...
}
}
public class Wrapper : DependencyObject
{
public static readonly DependencyProperty CanBeValidatedProperty =
DependencyProperty.Register(nameof(CanBeValidated), typeof(bool),
typeof(Wrapper));
public bool CanBeValidated
{
get { return (bool)GetValue(CanBeValidatedProperty); }
set { SetValue(CanBeValidatedProperty, value); }
}
}
Finally, you'll also need a binding proxy object that captures the DataContext where the source property is defined:
public class BindingProxy : System.Windows.Freezable
{
protected override Freezable CreateInstanceCore()
{
return new BindingProxy();
}
public object Data
{
get { return (object)GetValue(DataProperty); }
set { SetValue(DataProperty, value); }
}
public static readonly DependencyProperty DataProperty =
DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new PropertyMetadata(null));
}
XAML:
<TextBox>
<TextBox.Resources>
<vRules:BindingProxy x:Key="proxy" Data="{Binding}"/>
</TextBox.Resources>
<TextBox.Text>
<Binding Path="myPath"
UpdateSourceTrigger="PropertyChanged"
ValidatesOnDataErrors="True">
<Binding.ValidationRules>
<vRules:RootPathValidationRule ValidatesOnTargetUpdated="True">
<vRules:RootPathValidationRule.Wrapper>
<vRules:Wrapper CanBeValidated="{Binding Data.ValidationEnabled,
Source={StaticResource proxy}}"/>
</vRules:RootPathValidationRule.Wrapper>
</vRules:RootPathValidationRule>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
Please refer to this article for details.
I want to add dynamic items with a datatemplate that contains a TextBlock control, but the text of the TextBlock control will be selected from a XAML ResourceDictionary. The staticresource name will be obtained based on the result of the binding value.
How can I do that?
I'm trying something like this, but doesn't works.
<DataTemplate x:Key="languageItemTemplate">
<ContentControl>
<StackPanel>
<TextBlock Text="{StaticResource {Binding ResourceName}}"></TextBlock>
<TextBlock Text="{DynamicResource {Binding ResourceName}}"></TextBlock>
</StackPanel>
</ContentControl>
</DataTemplate>
UPDATE
Thanks to Tobias, the fist option of his answer works. But I need to instance the converter first to get it work. Which one is the best idea to do that?
In the application_startup method and use it for all the application or in the Window.Resources of the window I use the converter?
Maybe a merge of both and do that on the Application.Resources?
thanks for your answer.
private void Application_Startup(object sender, StartupEventArgs e)
{
LoadConverters();
}
private void LoadConverters()
{
foreach (var t in System.Reflection.Assembly.GetExecutingAssembly().GetTypes())
{
if (t.GetInterfaces().Any(i => i.Name == "IValueConverter"))
{
Resources.Add(t.Name, Activator.CreateInstance(t));
}
}
}
OR
<local:BindingResourceConverter x:Key="ResourceConverter"/>
<DataTemplate x:Key="languageItemTemplate">
<ContentControl>
<StackPanel>
<TextBlock Text="{Binding Name, Converter={StaticResource ResourceConverter }}" />
</StackPanel>
</ContentControl>
</DataTemplate>
If the resource is an application level resource you could simply use a converter to convert from the resource name to the actual object like this:
public class BindingResourceConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string resourceKey = value as string;
if (!String.IsNullOrEmpty(resourceKey))
{
var resource = Application.Current.FindResource(resourceKey);
if (resource != null)
{
return resource;
}
}
return Binding.DoNothing;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
And use it like this:
<TextBlock Text="{Binding ResourceKey, Converter={StaticResource ResourceConverter}}" />
If the resource is in a local scope, we need a reference to the control to search its resources. You can get the resource name and the control by using an attached property:
public class TextBlockHelper
{
public static readonly DependencyProperty TextResourceKeyProperty =
DependencyProperty.RegisterAttached("TextResourceKey", typeof(string),
typeof(TextBlockHelper), new PropertyMetadata(String.Empty, OnTextResourceKeyChanged));
public static string GetTextResourceKey(DependencyObject obj)
{
return (string)obj.GetValue(TextResourceKeyProperty);
}
public static void SetTextResourceKey(DependencyObject obj, string value)
{
obj.SetValue(TextResourceKeyProperty, value);
}
private static void OnTextResourceKeyChanged(
DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
string resourceKey = e.NewValue as string;
if(d is TextBlock tb)
{
var r = tb.TryFindResource(resourceKey);
if (r != null)
{
tb.Text = r.ToString();
}
}
}
}
And you can use it like this:
<Grid>
<Grid.Resources>
<sys:String x:Key="SomeLocalResource">LocalResource</sys:String>
</Grid.Resources>
<TextBlock h:TextBlockHelper.TextResourceKey="{Binding ResourceKey}" />
</Grid>
I have a DependencyProperty in my UserControl with a property changed callback. The property works as expected and the callback works as expected.
public double CurrentFlow
{
get { return (double)GetValue(CurrentFlowProperty); }
set { SetValue(CurrentFlowProperty, value); }
}
public static readonly DependencyProperty CurrentFlowProperty = DependencyProperty.Register("CurrentFlow", typeof(double), typeof(MyUserControl), new PropertyMetadata(0.0, OnCurrentFlowPropertyChanged));
private static void OnCurrentFlowPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
{
Console.WriteLine("CurrentFlow changed.");
}
However, I have a TextBlock in my UserControl where I want to display CurrentFlow as a formatted string. Currently, I have the Text property of the TextBlock binded to CurrentFlow, and it works, but I'm not getting the format I need. (Too many numbers after the decimal.)
<TextBlock Text="{Binding Path=CurrentFlow, RelativeSource={RelativeSource AncestorType=UserControl}}" />
Ideally, I'd like to have a property named CurrentFlowString that takes the value from CurrentFlow and formats it to what I want. For example: CurrentFlow.ToString("0.00");
What's the best way to go about this with DependencyProperties? I know how to do this with regular properties but I'm kinda stuck here.
Thanks!
If you want to have more flexibility than using StringFormat, you can also use a custom converter. For example,
public class MyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is double d)
return $"{d:f2}";
return null;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}
Then add it to your UserControl.Resources, and use it in your Binding:
<UserControl.Resources>
<local:MyConverter x:Key="MyConverter" />
</UserControl.Resources>
<Grid>
<TextBlock Text="{Binding Path=CurrentFlow, RelativeSource={RelativeSource AncestorType=UserControl}, Converter={StaticResource MyConverter}}" />
</Grid>
Solution 2:
Based on your comment below, here's an alternative solution. First, create a new dependency property; for example, FormattedCurrentFlow:
public static readonly DependencyProperty FormattedCurrentFlowProperty = DependencyProperty.Register(
"FormattedCurrentFlow", typeof(string), typeof(MyControl), new PropertyMetadata(default(string)));
public string FormattedCurrentFlow
{
get { return (string)GetValue(FormattedCurrentFlowProperty); }
set { SetValue(FormattedCurrentFlowProperty, value); }
}
Since you already have a method to handle changes in CurrentFlow, update the new FormattedCurrentFlow when CurrentFlow changes:
private static void OnCurrentFlowPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
{
var myControl = (MyControl)source;
myControl.FormattedCurrentFlow = $"{myControl.CurrentFlow:f2}";
}
The TextBox in the UserControl can now bind to FormattedCurrentFlow:
<TextBlock Text="{Binding Path=FormattedCurrentFlow, RelativeSource={RelativeSource AncestorType=UserControl}}" />
Binding to double may produce following validation error
Value ... could not be converted.
When using ExceptionValidationRule errors are more talkative:
Input string was not in a correct format.
Value was either too big or too small for a ...
Perhaps there are more. Add to them those what I can throw myself in bound property setter.
Now, I want to localize those messages (preferably second version). Not a big surprise, but sources doesn't reveal anything useful (am I looking at wrong place?).
I can make my own validation rules, but perhaps there is an easier way?
My question: can I localize ExceptionValidationRule?
Below is mcve:
xaml:
<TextBox>
<TextBox.Text>
<Binding Path="TestDouble" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<!--<local:MyValidationRule />-->
<!--<ExceptionValidationRule />-->
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
<Validation.ErrorTemplate>
<ControlTemplate>
<TextBlock Margin="0,20,0,0" Foreground="Red" Text="{Binding ErrorContent}" />
</ControlTemplate>
</Validation.ErrorTemplate>
</TextBox>
cs:
public partial class MainWindow : Window
{
public double TestDouble { get; set; }
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
}
public class MyValidationRule : ValidationRule
{
public override ValidationResult Validate(object value, CultureInfo cultureInfo) => ValidationResult.ValidResult; // not used
public override ValidationResult Validate(object value, CultureInfo cultureInfo, BindingExpressionBase owner)
{
var bindingExpression = owner as BindingExpression;
if (bindingExpression != null)
{
var type = bindingExpression.ResolvedSource.GetType().GetProperty(bindingExpression.ResolvedSourcePropertyName).PropertyType;
if (type == typeof(double))
{
double result;
if (!double.TryParse((string)value, out result))
return new ValidationResult(false, "The value format is not recognized"); // custom message
}
... // and so on, for all types ?????
}
return base.Validate(value, cultureInfo, owner);
}
}
To localize such error messages, which appears during updating source of binding, its enough to setup UpdateSourceExceptionFilter callback handler of binding, no custom validation rule is needed (ExceptionValidationRule is required).
xaml:
<Binding UpdateSourceExceptionFilter="ExeptionFilter" ...>
cs:
object ExeptionFilter(object bindingExpression, Exception exception)
{
return "Localized error message";
}
Obviously it can be switch/case (in C# 7, earlier - if/else if) to provide exception-specific messages (in my question those are FormatException and OverflowException correspondingly).
Suppose you have a class inheriting from ValidationRule:
public class MyValidationRule : ValidationRule
{
public string ValidationType { get; set; }
public override ValidationResult Validate(object value, CultureInfo cultureInfo) {}
}
In XAML you are validating like this:
<ComboBox.SelectedItem>
<Binding Path="MyPath" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged" NotifyOnValidationError="True">
<Binding.ValidationRules>
<qmvalidation:MyValidationRule ValidationType="notnull"/>
</Binding.ValidationRules>
</Binding>
</ComboBox.SelectedItem>
Which works and everything is ok.
But suppose now, you want to have ValidationType="{Binding MyBinding}" where MyBinding comes from DataContext.
For this purpose I would need to make MyValidationRule as a DependencyObject and add a Dependency Property.
I've tried to write a class that is DependencyObject, and bind it. There are 2 problems though.. the ValidationRule DOES NOT have the DataContext from the Combobox / Item.
Do you have any ideas, on how to solve that?
Since ValidationRule does not inherit from DependencyObject you cannot create a DependecyProperty in your custom validation class.
However as explained in this link you can have a normal property in your validation class which is of a type that inherits from DependecyObject and create a DependencyProperty in that class.
For example here is a custom ValidationRule class that support bindable property:
[ContentProperty("ComparisonValue")]
public class GreaterThanValidationRule : ValidationRule
{
public ComparisonValue ComparisonValue { get; set; }
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
string s = value?.ToString();
int number;
if (!Int32.TryParse(s, out number))
{
return new ValidationResult(false, "Not a valid entry");
}
if (number <= ComparisonValue.Value)
{
return new ValidationResult(false, $"Number should be greater than {ComparisonValue}");
}
return ValidationResult.ValidResult;
}
}
ComparisonValue is a simple class that inherits from DependencyObject and has a DependencyProperty:
public class ComparisonValue : DependencyObject
{
public int Value
{
get { return (int)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
nameof(Value),
typeof(int),
typeof(ComparisonValue),
new PropertyMetadata(default(int));
This solves the original problem but unfortunately brings two more problems:
The binding does not work correctly since the ValidationRules is not part of visual tree and therefore cannot get the bound property correctly. For example this naive approach will not work:
<TextBox Name="TextBoxToValidate">
<TextBox.Text>
<Binding Path="ViewModelProperty" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<numbers:GreaterThanValidationRule>
<numbers:ComparisonValue Value="{Binding Text, ElementName=TextBoxToValidate}"/>
</numbers:GreaterThanValidationRule>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
Instead a proxy object should be used as explained in this answer:
<TextBox Name="TextBoxToValidate">
<TextBox.Resources>
<bindingExtensions:BindingProxy x:Key="TargetProxy" Data="{Binding Path=Text, ElementName=TextBoxToValidate}"/>
</TextBox.Resources>
<TextBox.Text>
<Binding Path="ViewModelProperty" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<numbers:GreaterThanValidationRule>
<numbers:ComparisonValue Value="{Binding Data, Source={StaticResource TargetProxy}}"/>
</numbers:GreaterThanValidationRule>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
BindingProxy is a simple class:
public class BindingProxy : Freezable
{
protected override Freezable CreateInstanceCore()
{
return new BindingProxy();
}
public object Data
{
get { return GetValue(DataProperty); }
set { SetValue(DataProperty, value); }
}
public static readonly DependencyProperty DataProperty = DependencyProperty.Register(nameof(Data), typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
}
If the property in custom ValidationRule is bound to another object's property, the validation logic for the original property will not fire when that other object's property changes.
To solve this problem we should update the binding when the ValidationRule's bound property is updated. First we should bind that property to our ComparisonValue class. Then, we can update the source of the binding when the Value property changes:
public class ComparisonValue : DependencyObject
{
public int Value
{
get { return (int)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register(
nameof(Value),
typeof(int),
typeof(ComparisonValue),
new PropertyMetadata(default(int), OnValueChanged));
private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ComparisonValue comparisonValue = (ComparisonValue) d;
BindingExpressionBase bindingExpressionBase = BindingOperations.GetBindingExpressionBase(comparisonValue, BindingToTriggerProperty);
bindingExpressionBase?.UpdateSource();
}
public object BindingToTrigger
{
get { return GetValue(BindingToTriggerProperty); }
set { SetValue(BindingToTriggerProperty, value); }
}
public static readonly DependencyProperty BindingToTriggerProperty = DependencyProperty.Register(
nameof(BindingToTrigger),
typeof(object),
typeof(ComparisonValue),
new FrameworkPropertyMetadata(default(object), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
}
The same proxy problem in the first case also exists here. Therefore we should create another proxy object:
<ItemsControl Name="SomeCollection" ItemsSource="{Binding ViewModelCollectionSource}"/>
<TextBox Name="TextBoxToValidate">
<TextBox.Resources>
<bindingExtensions:BindingProxy x:Key="TargetProxy" Data="{Binding Path=Items.Count, ElementName=SomeCollection}"/>
<bindingExtensions:BindingProxy x:Key="SourceProxy" Data="{Binding Path=Text, ElementName=TextBoxToValidate, Mode=TwoWay}"/>
</TextBox.Resources>
<TextBox.Text>
<Binding Path="ViewModelProperty" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<numbers:GreaterThanValidationRule>
<numbers:ComparisonValue Value="{Binding Data, Source={StaticResource TargetProxy}}" BindingToTrigger="{Binding Data, Source={StaticResource SourceProxy}}"/>
</numbers:GreaterThanValidationRule>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
In this case the Text property of TextBoxToValidate is validated against the Items.Count property of SomeCollection. When the number of items in the list changes, the validation for the Text property will be triggered.