Programming with .NET - General

Re: Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

joji777 — Sat, 11 Apr 2009 09:26:55 GMT

Hi,

See "odegaard" post of this date

09-11-2008 7:36 PM

in my post, in given code,,,, checck page.Dispathcer..................

Re: Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

SharpGIS — Sat, 11 Apr 2009 02:07:12 GMT

Errrrr and that has what to do with the DepedencyObject constructor was internal at the beta release (ie. can't inherit from it) ?

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

joji777 — Sat, 11 Apr 2009 01:40:32 GMT

Well I am using SL2 and it is not working. I can see at front of my eyes. What I am trying to do its,

I have a Page class, then I created another class which has method to create a button and on that button click you select a file to upload on my server, all this functionality in my Uploader class, this also update the progress of uploading. This Uploader class has 2 public methods, one creates button and other creates a text block (its text i want to update to show progress.)

I call this create button and create text method in Page by creating instance of Uploader class in a for loop and create 4 buttons and text blocks for each button. Now in uploader class i have to write following code

private static Page page = new Page();
page.Dispatcher.BeginInvoke(new Action(() =>
{
var textBlock = page.mygrid.FindName("uploading_grid_textblok_1") as TextBlock;
textBlock.Text = string.Empty;
textBlock.Text += statusstring;
}));

This does not work, I tried all possible ways, and it does not work, now i am working on another way which works partialy but still not reliable. Above mentioned code will give you different errors on different changes.

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

SharpGIS — Sat, 11 Apr 2009 01:27:41 GMT

How can this be a limitation for you, when this limitation has been removed since SL2 was released in its final state? This is an old beta issue.

Re: Inheritance limitation (FrameworkElement & DependencyObject)

joji777 — Sat, 11 Apr 2009 00:44:03 GMT

I am also badly stuck because of this problem, and so far I spent more than 3 days tpo find a solution and unable to find one. I am in great favor to finish this limitation and inheritance should be allowed.

Re: Inheritance limitation (FrameworkElement & DependencyObject)

SharpGIS — Sat, 28 Mar 2009 17:09:27 GMT

It was an SL2 beta issue, and has been possible since Silverlight 2RTW.

Re: Inheritance limitation (FrameworkElement & DependencyObject)

avbersSL — Sat, 28 Mar 2009 13:33:08 GMT

Is this allowed in SL3 now??

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Odegaard — Thu, 11 Sep 2008 23:36:38 GMT

I'll cast a vote as well !

I'm currently working on an API and there are sooo many cases where i'd like to use dependency object.

Right now I have two options:

Just create a class (not inheriting). This has the downside of not being able to use FindName on the object and modify it at runtime.
Inherit from control. This confuses the developer because he gets a zillion properties that have absolutely no effect.

Both options are really poor solutions for a good API.

Re: Inheritance limitation (FrameworkElement & DependencyObject)

asterite — Fri, 25 Jul 2008 15:11:45 GMT

I want to add my vote for this. I need to do an animation on one of my objects, which is *not* visible in the UI. This object implements INotifyPropertyChanged and listeners are registered to that which do update the UI. I really can't understand why DependencyObject can't be subclassed by us.

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

xiard — Mon, 09 Jun 2008 20:27:33 GMT

I'll go ahead and add my vote as well to allow inheritance from DependencyObject a la WPF. I'm trying to create a custom class that will be used in an IEnumerable to bind to a DataGrid. The columns of the DataGrid would bind to the DependencyProperties I create in this custom class. Essentially, the custom DependencyObject subclass would be the DataContext of the items bound via the DataGrid ItemsSource property. Since I would obviously have one instance of my custom class per row in the DataGrid, I want the rows to be as light-weight as possible. I'm going to go ahead and derive my subclass from Control and see how far I get, but I certainly was surprised to find out that I couldn't derive from DependencyObject.

Thanks,

David Cater

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Kevmeister — Fri, 06 Jun 2008 06:36:11 GMT

I have only just run into this problem myself (wanting to derive from DependencyObject, to use the dependency properties system).

I also vote that it should be possible to derive from DependencyObject.

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

PatriceVB — Tue, 27 May 2008 21:07:18 GMT

Common Guy! You may be right about the frameworkelement but what about the DependencyObject but do you think that it is normal to have to inherit from the control class to be able to implement dependency properties? We should at least be able to inherits from dependency objects to gain the ability to use the features provided by Silverlight like the animations without having to create a control for that like what we can do in WPF :)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Eric Willeke — Tue, 27 May 2008 20:59:29 GMT

The biggest thing I've wanted to do was to define a data object that can host Dependency Properties that can then easily participate in data binding. The specific design case isn't the strongest currently, but it's a pattern that I've used consistently in WPF applications to great effect. As it stands, I'm approximating it through post-construction assignment.

Having dug into it more than I had when I originally posted this comment, I'm not entirely sure the current data binding support handles the cases that I was attempting to pursue anyway, but in the long run this would be useful.

Clarification, I was attempting to subclass DependencyObject, not FrameworkElement. Also, making OnPropertyChanged "internal protected virtual" would open up a lot of the event handling and abstraction I was also hoping to accomplish with using DependencyObject.

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Dave Relyea — Tue, 27 May 2008 20:36:02 GMT

What sorts of things do you want to do with your subclasses? Note that subclassing FrameworkElement is not all that useful, because we don't support low-level drawing primitives, so you have to encapsulate other elements.

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

tonypujals — Wed, 21 May 2008 20:27:49 GMT

I want to cast my vote for removing the limitation as well.

Programming with .NET - General

Re: Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement &amp; DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)

Re: Re: Inheritance limitation (FrameworkElement & DependencyObject)