Open-Source dependency property system
- Properties
- normal, read-only, attached, attached + read-only
- Handlers and values all use generics to avoid unnecessary casts
- Can have a DependencyExtension attached for value manipulation.
- Supports the following features
- Value-coercing: Coerces the value of a property
- Value-validation: Validates the value before changing it
- Property-changing: Executes code before the value is going to change
- Property-changed: Executes code when the value has been changed
- Property memory consumption reduced as only non-default values require storing of the actual value.
- IDependencyObject allows implementation when you cannot modify the base object.
- Multithreading-support ( access checks are supported already by inheriting from DependencyObjectContainer/DependencyObject and overwriting "CheckPropertyAccess" )
- Property-Bindings
- Serialization-Deserialization
- Animations
Dependency-Object with two properties where one of them is read-only.
public class Sample : DependencyObject
{
public static readonly DependencyProperty<String> NameProperty = DependencyProperty.Create<Sample, String>(p => p.Name, String.Empty);
static readonly DependencyPropertyKey<DateTime> TimeOfCreationPropertyKey = DependencyProperty.CreateReadonly<Sample, DateTime>(p => p.TimeOfCreation);
public static readonly DependencyProperty TimeOfCreationProperty = TimeOfCreationPropertyKey.Property;
public String Name
{
get => GetValue(NameProperty);
set => SetValue(NameProperty, value);
}
public String TimeOfCreation
{
get => GetValue(TimeOfCreationProperty);
private set => SetValue(TimeOfCreationPropertyKey, value);
}
public Sample() => TimeOfCreation = DateTime.Now;
}You can use the dependency property system in existing projects which already provide base classes without modifying those. To do so you've to implement the IDependencyObject interface.
public abstract class MvvmDependencyObject : MvvmBase, IDependencyObject
{
readonly DependencyObjectContainer _DependencyObjects;
public MvvmDependencyObject() => _DependencyObjects = new DependencyObjectContainer(this);
#region IDependencyObject Implementation
// Implement IDependencyObject here
#endregion
}Reacting to changes of a dependency-property:
public void CreateSample()
{
Sample sample = new Sample();
sample.AddChangeHandler(Sample.NameProperty, Sample_NameChanged);
sample.Name = "Jonny"; // Prints "Jonny"
// Remove the change handler
sample.RemoveChangeHandler(Sample.NameProperty, Sample_NameChanged);
// Add a change handler which reacts to all property changes
sample.PropertyChanged += Sample_PropertyChanged;
sample.Name = "Jonny"; // No change -> Nothing happens
sample.Name = "Dude"; // Prints "Name: Dude"
}
void Sample_NameChanged(IDependencyObject sender, PropertyChangedEventArgs<String> args)
{
// Called when the property has been changed
Console.WriteLine(args.NewValue);
}
void Sample_PropertyChanged(IDependencyObject sender, PropertyChangedEventArgs args)
{
// Called when any property has been changed
Console.WriteLine($"{args.Property.Name} {args.NewValue}");
}Property-validation ( ensures "Name" is never null ):
public class ValidationSample : DependencyObject
{
public static readonly DependencyProperty<String> NameProperty = DependencyProperty.Create<ValidationSample, String>(p => p.Name, String.Empty, validation:(s, v) => v != null);
public String Name
{
get => GetValue(NameProperty);
set => SetValue(NameProperty, value);
}
}Property-coercion ( forces the "Age" to be in the range between 0 and 200, the base value still can be different ):
public class CoerceSample : DependencyObject
{
public static readonly DependencyProperty<Int32> AgeProperty = DependencyProperty.Create<Sample, String>(p => p.Age, 0, coerceValue:(s, v) => Math.Min(200, Math.Max(0, v)));
public Int32 Age
{
get => GetValue(AgeProperty);
set => SetValue(AgeProperty, value);
}
}Author: Felix Klakow