Comments on: Very simple MVVM demo application

By: Jeremy

Jeremy — Tue, 20 Jul 2010 08:56:50 +0000

This sample application is designed to work with WPF, not Silverlight. That’s the reason why I’m suggesting you to take a look at an MVVM framework which supports Silverlight.

By: Debashish Gupta

Debashish Gupta — Tue, 20 Jul 2010 08:54:50 +0000

Hi Jeremy ,
Not sure , why are u telling me to use MVVM Framework.
As i see ur downloadable application works fine.
I cannot add dlls like PresentationFramework.dll etc.
Regards
Debashish.

By: Jeremy

Jeremy — Tue, 20 Jul 2010 07:35:56 +0000

Debashish,

You don’t have the exact same set of functionalities in Silverlight and WPF. That’s why you have error with CommandManager and TypeDescription.

Please take a look at a MVVM frameworks which supports Silverlight in order to see a working implementation of the ICommand interface. For example, you can look at the MVVM Light Toolkit (http://mvvmlight.codeplex.com) and its RelayCommand class (http://mvvmlight.codeplex.com/SourceControl/changeset/view/47157#750822).

Hope this helps

By: Debashish Gupta

Debashish Gupta — Mon, 19 Jul 2010 14:35:13 +0000

Hi , I was trying to go through it.
But i could not make
CommandManager.RequerySuggested += value;
work as it was not able to find the CommandManager
—————–
and
if (TypeDescriptor.GetProperties(this)[propertyName]
in ViewModelBase
work as its not able to find the TypeDescriptor in System.ComponentModel.

I was trying to make a Silverlight Project and trying to make it run.

Regards
Debashish.

By: Damian

Damian — Thu, 15 Jul 2010 12:51:35 +0000

Ok, I see now It changes but after selecting again from list. But in other way. So thank you very much My weekend will be happier thanks your article ! Have a nice weekend, too

By: Jeremy

Jeremy — Thu, 15 Jul 2010 12:11:17 +0000

I just did the test: if I change the second TextBox in the DetailView to display the Age property, and without the correct OnPropertyChanged, any changes in the first TextBox is not reflected in the second TextBox.

However, adding the OnPropertyChanged fix this issue.

By: Damian

Damian — Thu, 15 Jul 2010 11:57:45 +0000

Thank You for help.

Unfortunately when I add second textbox linked with Age property everything works ok. So I convert ObservableCollection to List, and removed inheritance from ViemModelBase from MasterViewModel and it still works. I appreciate that you have time for me. I’m very newbie.

By: JAPF » Blog Archive » Where does the default TwoWay binding comes from ?

Thu, 15 Jul 2010 11:50:47 +0000

[...] got a comment on my post about a very simple MVVM application about the fact that removing the TwoWay mode on a binding did not change the behavior of the [...]

By: Jeremy

Jeremy — Thu, 15 Jul 2010 11:35:48 +0000

Damian,

About the OnPropertyChanges(“FirstName”) with the Age property it’s a mistake. It should be “Age” of course.

About the TwoWay binding it depends actually on the associated DependencyProperty of the control. In a TextBox, the Text property is declared with the BindsTwoWayByDefault option which explain why removing the explicit TwoWay does not change the behavior.

Finally, about the OnPropertyChanged, you can’t see the benefits in this demo because I’m not demonstrating this synchronization. But if for example you put 2 TextBoxes linked with the same property (ie. Age) you’ll see that without the OnPropertyChanged only one will be refreshed.

Hope this helps !

By: Damian

Damian — Thu, 15 Jul 2010 09:43:47 +0000

More, I even removed inheritance from ViewModelBase and Mode=TwoWay and still works fine. I’m little confused :/