Silverlight Challenge: Creating a DependencyProperty - Christopher Bennage - Devlicio.us

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Christopher Bennage » Silverlight Challenge: Creating a DependencyProperty

Silverlight Challenge: Creating a DependencyProperty

The following code throws an exception. Can you spot the bug?

public class MyControl : Control
{
    public static DependencyProperty MyPropertyProperty = DependencyProperty.Register(
        "MyProperty",
        typeof (double),
        typeof (MyControl),
        new PropertyMetadata(0));

    public double MyProperty
    {
        get { return (double) GetValue(MyPropertyProperty); }
        set { SetValue(MyPropertyProperty, value); }
    }
}

Posted 03-09-2010 3:36 PM by Christopher Bennage

Filed under: Silverlight, Challenge

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Comments

Hüseyin Tüfekçilerli wrote re: Silverlight Challenge: Creating a DependencyProperty

on 03-09-2010 4:15 PM

Use

new PropertyMetadata(0d)

instead of

new PropertyMetadata(0)

Jason Young wrote re: Silverlight Challenge: Creating a DependencyProperty

on 03-09-2010 4:16 PM

I can see two issues, the dependency property declaration should be marked readonly and the value passed to the PropertyMetadata should be a double, i.e. "0.0".

Cadred (dotNET) wrote dotNet News

on 03-09-2010 4:23 PM

dotNet News

Hadi wrote re: Silverlight Challenge: Creating a DependencyProperty

on 03-10-2010 3:48 AM

the only change needed is "new PropertyMetadata(0.0)", readonly is not necessarily needed.

Christopher Bennage wrote re: Silverlight Challenge: Creating a DependencyProperty

on 03-10-2010 10:17 AM

Correct. The default needs to be a double. The exception throw is a little vague, and I stared at this for about 10 minutes before it occurred to me. :-P

Regarding the 'readonly', it doesn't cause an exception but it's a good idea. It was an accident that I omitted it in the example.

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