CODEWITHSUNDEEP
c#wpfxaml
Michael Smits
Michael Smits

Reputation: 301

How can I set a default value for a dependency property of type derived from dependencyobject?

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'.

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 <Setter> 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

Upvotes: 30

Views: 28393

Answers (3)

user8604852
user8604852

Reputation: 1

public static readonly DependencyProperty BackgroundColorProperty = DependencyProperty.Register("BackgroundColor", typeof(Brush), typeof(YinaKassaProductButtonCustomControl), new PropertyMetadata(null));

The default value needs to be immutable, so you can't set it to the value of another dependency property.

I myself ended up adding a property to my class like this

public Brush BorderColor => IsSelectedBorderColor ?? BackgroundColor;

Then I bind to the BorderColor in my template of my custom control. Basicly it checks if the dependency property IsSelectedBorderColor is not null and uses its value, else it uses the value of the BackgroundColor dependency property.

I use it in my triggers...

<ControlTemplate.Triggers>
    <Trigger Property="IsSelected" Value="True">
        <Setter Property="Background" Value="Transparent"></Setter>
        <Setter Property="Foreground" Value="White"></Setter>
        <Setter Property="BorderBrush" Value="{Binding BorderColor, RelativeSource={RelativeSource Self}}"></Setter>
    </Trigger>
    <Trigger Property="IsSelected" Value="False">
        <Setter Property="Background" Value="{Binding BackgroundColor, RelativeSource={RelativeSource Self}}"></Setter>
        <Setter Property="Foreground" Value="{Binding ForegroundColor, RelativeSource={RelativeSource Self}}"></Setter>
        <Setter Property="BorderBrush" Value="{Binding BackgroundColor, RelativeSource={RelativeSource Self}}"></Setter>
    </Trigger>
</ControlTemplate.Triggers>

Upvotes: 0

Zahid Sattar
Zahid Sattar

Reputation: 1517

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"));

Upvotes: 47

Yakoob Hammouri
Yakoob Hammouri

Reputation: 125

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));
}

Upvotes: 8

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