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I am new to WPF and this is my first post. I have created a class called 'Fruit' that descends from 'DependencyObject' and adds and extra property called 'Apple'. I have created a new custom control that includes a Dependency Property called 'MyFruit' of type 'Fruit'. My question is, how can i set the default value for the properties within 'MyFruit' object (i.e. the 'Apple' property? I would like to set this in XAML using the object.
public class Gauge : Control { . . . //--------------------------------------------------------------------- #region MyFruit Dependency Property public Fruit MyFruit { get { return (Fruit)GetValue(MyFruitProperty); } set { SetValue(MyFruitProperty, value); } } public static readonly DependencyProperty MyFruitProperty = DependencyProperty.Register("MyFruit", typeof(Fruit), typeof(CircularGauge), null); #endregion } //------------------------------------------------------------------------- #region Fruit class public class Fruit : DependencyObject { private int apple; public int Apple { get { return apple; } set { apple = value; } } } #endregion 
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When you define a custom XAML dependency property, one of the things you do is specify the default value. You can do this by providing the default value directly: DependencyProperty. Register("MyProperty", propertyType, ownerType, new PropertyMetadata(defaultValue));
A dependency property can reference a value through data binding. Data binding works through a specific markup extension syntax in XAML, or the Binding object in code. With data binding, determination of the final property value is deferred until run time, at which time the value is obtained from a data source.
Dependency properties are properties that are registered with the WPF property system through Register or RegisterReadOnly calls. The Register method returns a DependencyProperty instance that holds the registered name and characteristics of a dependency property.
A Dependency Property is a property whose value depends on the external sources, such as animation, data binding, styles, or visual tree inheritance. Not only this, but a Dependency Property also has the built-in feature of providing notification when the property has changed, data binding and styling.
Instead of null in your dependency property metadata insert
new UIPropertyMetadata("YOUR DEFAULT VALUE GOES HERE") So now it becomes
public static readonly DependencyProperty MyFruitProperty = DependencyProperty.Register("MyFruit", typeof(Fruit), typeof(CircularGauge), new UIPropertyMetadata("YOUR DEFAULT VALUE GOES HERE")); You need to use PropertyMetaData like this:
class MyValidation { public bool status { get { return (bool)GetValue(statusProperty); } set { SetValue(statusProperty, value); } } public static readonly DependencyProperty statusProperty = DependencyProperty.Register("status", typeof(bool), typeof(MyValidation),new PropertyMetadata(false)); } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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