SilverlightShow: ModalDialogs, IEditableObject and MVVM in Silverlight 4 Comments

Re: ModalDialogs, IEditableObject and MVVM in Silverlight 4

geertd — Sun, 04 Dec 2011 15:40:09 GMT

Maybe you don't need to:

Another approach is to break this problem down into more manageable pieces:

- A CompanyList VM and V for the company list
- A Company VM and V for handing the Company properties and the list of EditableEmployees (Employee wrapped in generic IEditableObject)
- A Employee VM and V for handling the Employee properties

The CompanyViewModel could have commands to add/remove/edit employees and these would create a EmployeeViewModel (and calling BeginEdit on the Employee in case of edit) and use that as datacontext of an EmployeeView shown in a model dialog, and handle the result of the modal dialog (calling CancelEdit on cancel, or EndEdit on OK)...

Re: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Sun, 04 Dec 2011 15:22:00 GMT

Hi geertd, you are right, the IEditableObject implemenation will not work in that scenario. It will require additional work to handle hierarchies.

Re: ModalDialogs, IEditableObject and MVVM in Silverlight 4

geertd — Sun, 04 Dec 2011 13:16:19 GMT

Suppose that you are working with a hierarchical structure e.g. a Company class that has a list of Persons. You select a Company from a list, open up a modal dialog to edit that company and start editing it: change the Company.Name, change the name of the first person of that company, add a new person... and then you want to cancel.

I don't think the generic implementation of IEditableObject handles such a hierarchy?

How would you handle such a case?

Re: ModalDialogs, IEditableObject and MVVM in Silverlight 4

mobygeek — Thu, 16 Jun 2011 14:06:03 GMT

clean work! excellent! could this be applied also for WPF and I mainly worked with DI frameworks (autofac) is there any particular reason you preffered MEF over DI Framerwork? as far as I know MEF's primary role is not about DI.

thanks

Re: ModalDialogs, IEditableObject and MVVM in Silverlight 4

eduaguiar281 — Thu, 09 Jun 2011 22:52:53 GMT

Thanks, your article is very good and helped me a lot, it was exactly what I needed.Sorry my bad English, I had to appeal to the google translator. Maybe not 100% correct.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

moakley — Fri, 14 Jan 2011 19:38:37 GMT

Issue resolved using mediator.

Thanks, moakley

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

moakley — Tue, 11 Jan 2011 16:48:29 GMT

I need the edit view model to call a web service and return data when completed. No problem with that. From the view model I then need to check the results of the web service call and then close if the results are good. So from the edit view model I somehow need to tell the view to close. Suggestions?

Thanks, moakley

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Mon, 13 Dec 2010 09:08:26 GMT

Hi Jim,

Sorry about the late reply. First about the RIA Services: Using RIA Services with my demo is not so difficult. All database (RIA service) calls should be placed in the PersonModel - the PersonModel should create a new instance (internally) of the RIA context and should expose methods for Load, Insert, Delete and Save. Here is the tricky moment, in WCF RIA all exposed business objects implements IEditableObject automatically. All changes are tracked in an EntityChangeSet object, and the changes are submitted collectively when you call SubmitChanges method of your domain context (respectively rejected, when you call the RejectChanges method).

About the second issue, I'm afraid I'm not able to help you unless I see some sample code.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Jim — Sun, 12 Dec 2010 00:46:16 GMT

Hi ppopadiyn,

I cloned your logic and changed it to become an option on menu. It worked fine first time entering the option but it crashed at "this.DataContext = value;" on the MainPage (which I changed to become an option instead of the startup page). Do you have any idea how to fix it? Thansk.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Jim — Thu, 02 Dec 2010 17:37:24 GMT

Hi ppopadiyn,

Can you give me some tips if I wanted to incorporate RIA service in your sample, what are the areas I should touch? How do I change PersonModel to pull data from domain service?

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Mon, 22 Nov 2010 11:01:41 GMT

Hi Jim,

Sorry but I am not a VB guy :(. However I would recommend you to use the following C# to VB converter. I'm using the demo version whenever I need to convert code and it works pretty reliable.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Jim — Fri, 19 Nov 2010 22:11:17 GMT

Hi ppopadiyn,

Is there a VB version for download? I tried to convert it from C# to VB but failed.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Thu, 18 Nov 2010 09:54:14 GMT

Hi Jim,

Thank you for your interest in the article. The project Framework is nothing special. It just contains common (reusable) classes. The purpose is at some point this library (these classes) to be re-used easy from another Silverlight project.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Jim — Wed, 17 Nov 2010 23:06:41 GMT

Hello,

It's very impressive and thank you for sharing your work.

My knowledge is Silverlight, MVVM is very limited. Can you tell what is required to create the project "Framework". Perhaps this is not target for beginner, if there is step by step instructions it will be wonderful.

Thanks anyway.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Fri, 17 Sep 2010 08:15:19 GMT

Hi J,

Happy to hear that you got things working ;)

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Fri, 17 Sep 2010 01:24:02 GMT

Hi Pencho,

I looked through some articles on MEF and was able to get things working.

Thanks again for your efforts !

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Thu, 16 Sep 2010 02:35:32 GMT

Thanks, Pencho. I was trying to sort the rest out by myself and not have to bother you again, but have just one question and some comments.

1. Exactly where should the this.DeleteControl.Value be placed?

2. I get the following messages in the ModalDialogWorker class after changing the parameter IModal modalview to the Lazy version:

'System.Lazy' does not contain a definition for 'Closed' and no extension method 'Closed' accepting a first argument of type 'System.Lazy' could be found (are you missing a using directive or an assembly reference?)

'System.Lazy' does not contain a definition for 'DataContext' and no extension method 'DataContext' accepting a first argument of type 'System.Lazy' could be found (are you missing a using directive or an assembly reference?)

And in the OnDeleteContactCommandExecute block I get the following 2 messages:

The best overloaded method match for 'Framework.IModalDialogWorker.ShowDialog<.....Contact>(Framework.IModalDialog, Framework.IModalView, ......Contact, System.Action<.......Contact>)' has some invalid arguments

cannot convert from 'System.Lazy' to 'Framework.IModalView'

PHEW! I do think i need to take some time to read up on MEF. If it is too much bother for you, i can switch to another implementation that does not use MEF for now, and convert later down the road.

Thanks !

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Wed, 15 Sep 2010 09:20:18 GMT

Hi again J,

Excellent case, you are doing nothing wrong. However there are several special features in mef, you should be familiar with. For example, when you call CompositionInitialized.SatisfyImport in your main control, this will create a new instance of your main viewmodel. On the next step, mef will try to satisfy all imports in your viewmodel. In your case probably it will need to create a new instance of the DeleteControl. Next, all imports in the DeleteControl will be satisfied. For example, your DeleteControl says: "Hey i want to import a string property to display on the UI" - this is DeleteContactWarning property. And of course, mef will try to find the corresponding export, which is located in your view model. And considering that your don't have selectedContact, it will throw NullReferenceExpcetion.

As you can note, all graph of objects are created immediately after the calling of SatisfyImport. If you have a long and complex graph of objects this can be expensive and unnecessary. In your case, this also is causing an exception. That's why mef supports so called lazy exports/imports. In order to use it all you need to do is to import an [System.Lazy] instead of [T] directly.

So, first in your ViewModel, instead of importing directly DeleteControl, you should have something like this:

[Import( ModalViewNames.DeleteControlName )]

public Lazy DeleteControl

{

get;

set;

}

When you use the DeleteControl, you should write something like this

this.DeleteControl.Value

In this case the instantiation of the DeleteControl will be delayed, until this.DeleteControl.Value is invoked. I suggest to put breakpoint in the DeleteControl constructor in the both cases, to see the difference.

Also you should slightly modify the logic about the constructing of the DeleteContactWarning message. Instead of import/export properties, you should import/export methods.

First, in your view model, you should construct the message in a method instead of property:

//[Export( "CustomDeleteMessage" )]

//public string DeleteMessage

//{

// get

// {

// return "Confirm permanent removal of " + this.SelectedPerson.Name;

// }

//}

[Export( "CustomDeleteMessage" )]

public string GetDeleteMessage()

{

return "Confirm permanent removal of " + this.SelectedPerson.Name;

}

Next, in the DeleteControl, you should have something like this:

public DeleteControl()

{

InitializeComponent();

this.Loaded += ( s, a ) =>

{

if ( this.CustomDeleteMessageAction != null )

{

this.tbMessage.Text = this.CustomDeleteMessageAction();

}

};

}

//[Import( "CustomDeleteMessage" )]

//public string CustomDeleteMessage

//{

// set

// {

// this.tbMessage.Text = value;

// }

//}

[Import( "CustomDeleteMessage" )]

public Func<string> CustomDeleteMessageAction

{

get;

set;

}

Again I suggest to try both of the solutions (import/export properties and methods) and see the difference. When you have import/export properties, it won't throw an exception, but i won't work correctly. E.g. try to delete more than one record - the delete message won't be construct correctly. If you use methods, everything should be o.k.

Hope this help.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Wed, 15 Sep 2010 02:56:58 GMT

Hi again, Ppopadyin

I used your code and it worked. I wanted to add further customization but due to the following line in my main control

if (!GalaSoft.MvvmLight.ViewModelBase.IsInDesignModeStatic)

{

// Use MEF To load the View Model

CompositionInitializer.SatisfyImports(this);

}

the entire ViewModel is loaded. I placed a variant of your code (not in the Constants.cs, as suggested) but in my ViewModel like so:

[Export("CustomDeleteMessage")]

public string DeleteContactWarning

{

get

{

return

"Confirm permanent removal of " +

this.selectedContact.FirstName + " " + this.selectedContact.LastName;

}

Unfortunately, this code segment is being executed before any Contact is selected. So i get a null exception message.

This is how my ViewModel starts:

[Export(ViewModelTypes.EmpContactViewModel)]

public class EmpContactViewModel: ViewModelBase, IPartImportsSatisfiedNotification

{

How can i delay the call to the DeleteContactWarning string till my SelectedContact has been set?

I tested the code after commenting out the SelectedContact names line, and i was able to get the custom message (minus the name, of course, to show in the dialog)

What am i doing wrong here?

Thanks again

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Tue, 14 Sep 2010 08:28:39 GMT

Hello J,

Here is a modified demo showing you how to pass custom delete message by using mef. Take a look at the following classes:

Code - behind for DeleteControl.xaml, I've added an additional property named "CustomDeleteMessage". See the [Import] attribute.
I've created an additional class named StringConfigurator - it is located in the Constants.cs file. There, the [Export] attribute is used. Note that, you should pass a contract name for both of the attributes. It must be the same in order to work.

Another possible solution is to create an additional class named DeleteControlViewModel - this will be a view model for the delete control. And in the DeleteControl, you will bind the TextBox.Text property to the corresponding string property of the DeleteControlViewModel. See the PersonViewModel, in the OnDeletePersonCommandExecute method. Instead of passing this.SelectedPerson as a DataContext to the DeleteControl you will pass a new instance of the DeleteControlViewModel. Personally I prefer the second solution. But the first one is also playable.

Please if you have any further questions do not hesitate to contact me.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Tue, 14 Sep 2010 03:49:44 GMT

Ppopadyin, I still need help with getting this example to work when sending a customized message to the dialog box using MEF. Can u give me some code. Looked at the link you provided but I'm still not getting it.

Thanks

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Mon, 13 Sep 2010 18:35:35 GMT

Thanks ppopadiyn!

Please ignore the duplicate post.

Cheers!

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Mon, 13 Sep 2010 09:54:17 GMT

Hello Jay,

I can think of three possible solutions

As you guessed, a parameter in the constructor of the control.
Add an additional property of type Hashtable (or generic Dictionary) in the IModalView interface.
If you want to use MEF, you could define "Property Imports" or use "Importing Constructor". Find more info here.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Jay — Mon, 13 Sep 2010 06:21:09 GMT

If I wanted to pass a string parameter to the DeleteControl in this situation, how would I go about it? I was thinking of passing a customized warning message to the control. I added the parameter in the constructor like this:

public DeleteControl (string myMessage)

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

jay — Mon, 06 Sep 2010 21:18:11 GMT

Great post! Your demo worked great.

I tried to use sections of it in my application. I keep getting the error message saying [Type of ......ModalDialog is not CLS_Compliant]. Any ideas ?

[Import]

public IModalDialog ModalDialog

{

get;

set;

}

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

stephan — Thu, 26 Aug 2010 15:17:50 GMT

well done

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Brian — Wed, 04 Aug 2010 16:39:22 GMT

There is a bug in your sample.

Select a Person.
Click Edit.
Modify the Name, and leave the focus in the Name text box.
Click the X in the upper right of the dialog to close it.
The Name was updated when it shouldn't have been.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Calabonga — Wed, 04 Aug 2010 03:20:38 GMT

Thank for your comment! That's what I realy need.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

dbis — Mon, 02 Aug 2010 20:26:59 GMT

Thanks!

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Mon, 02 Aug 2010 08:01:03 GMT

Hi dbis

Setting the DialogResult property of the ChildWindow, automatically close it (that is the behavior of the ChildWindow). That happens in the ModalDialogWorker, line 40.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

dbis — Mon, 02 Aug 2010 00:21:25 GMT

ppopadyyn, could you please clarify how you close modal dialog? Snippet

modalDialog.Close() is commented out

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Richard — Wed, 21 Jul 2010 13:15:11 GMT

ppopadyyn

Thanks for the prompt reply, okay I will look into further and hopefully resolve.

If anyone else has converted this code to Vb.net please get back to me.

Thanks

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Wed, 21 Jul 2010 11:37:34 GMT

Hi Richard,

Sorry but I am not an expert in VB.NET. As regards your question about the ExtendedChildWindow and IModalDialog. The ExtendedChildWindow class derives from ChildWindow and implements the IModalDialog interface. "it should have a Close() method - the C# version does not" - you are absolutely right there must be a Close method in the ExtendedChildWindow dialog, but it doesn't exists. However the base ChildWindow class has a Close method, or in other words the Close method is implemented in the base ChildWindow class, and the compiler obviously is pretty smart :) to recognize this. Just for a test you could rename the "Close" method in the C# code, for example to "Close2" and see the result, now you will have a compiler error.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Richard — Wed, 21 Jul 2010 11:25:11 GMT

I've converted your code to vb.net but am getting issues. I'm not an expert on OOP/classes...this is 2 examples errors (about 19 similiar)

Class 'PersonViewModel' must implement 'Sub OnImportsSatisfied()' for interface 'System.ComponentModel.Composition.IPartImportsSatisfiedNotification'. ..\...\Demo\ViewModels\PersonViewModel.vb

Class 'ExtendedChildWindow' must implement 'Sub Close()' for interface 'Framework.IModalDialog'. Views\ExtendedChildWindow.vb

My understanding is that as the ExtendedChildWindow implements Framework.IModalDialog
it should have a Close() method - the C# version does not - likewise the OnImportsSatisfied sub exists in PersonViewModel
but does not have the keyword 'Implements IPartImportsSatisfiedNotification' attached to it (C# version has this missing as well but no compilation error). If I add Implements IPartImportsSatisfiedNotification to the OnImportsSatisfied
sub I still get compilation error - I am now confused. Anyone one of you guru's shed some light/advice on this (obviouslt some difference in conversion from C# to Vb.net??)

Great article.

Richard

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Wed, 21 Jul 2010 10:53:55 GMT

Hello Calabonga,

Fortunately, in WCF RIA all exposed business objects implements IEditableObject automatically. All changes are tracked in an EntityChangeSet object, and the changes are submitted collectively when you call SubmitChanges method of your domain context (respectively rejected, when you call the RejectChanges method). So you could use the same approach with the modal dialogs and mvvm. The only difference is that you should work directly with your domain context.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Calabonga — Mon, 19 Jul 2010 03:49:41 GMT

Very good article! Thanks for your shared code.

But what about MVVM + RIA Services modal dialog and IEditableObject?

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Thanigainatahn — Sat, 05 Jun 2010 21:02:15 GMT

Hi There,

Very nice article.Good oppotunity to learn the Patterns.

Thanks,

Thani

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Alex — Sat, 05 Jun 2010 14:52:35 GMT

Very good article. Nice and clean solution.

I have one question, what to do with collections (collection of objects|)?

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Wed, 02 Jun 2010 18:43:41 GMT

Hi Denis, I am very happy you find the samples useful and thanks a lot for the improvements ;)

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Denis Vuyka — Wed, 02 Jun 2010 18:39:24 GMT

This is a great solution and your samples help me a lot. However I've made some corrections to code:

1. Some value comparison will work differently for reference and value types. So I've restricted Memento and Proxy with a constraint: "where T : class"

2. Memento won't work properly for the class containing properties with non-public setters (at least for Silverlight 3). I've updated the Memento.InitializeMemento with additional check for public setter presence:

foreach (var property in propertyInfos)
      {
        if (property.GetSetMethod() == null) continue;
        _storedProperties[property] = property.GetValue(originator, null);
      }

Regards,

Denis

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Fri, 21 May 2010 10:27:18 GMT

Hi aitran, probably, you need pass somehow to the ViewModel instances of the implementations (for example you can create a new constructor for the view model and pass instances of the ModalDialogWorker, ModalDialog, ModalView, etc). If you don't use MEF, then this is the nature of .Net, it will not create instances of these classes and when you try to use them NullReferenceException will be thrown. Let me know if this works for you.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

aitran — Fri, 21 May 2010 10:22:08 GMT

Im not using MEF for the whole solution, and I try to use IModalDialog, then it throws an exception of null in the ViewModel ModalDialogWorker

Please help,

Thanks.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Andre Baltieri — Fri, 21 May 2010 05:09:33 GMT

Amazing solution. A little complex to me yet, but will continue my studies on MVVM and MEF with SL.
This will realy help me a lot!

Thanks man!

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

mike kidder — Tue, 18 May 2010 03:23:45 GMT

Pencho, thanks for sharing this elegant solution, source code, and well written article....

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

ppopadiyn — Wed, 12 May 2010 17:16:48 GMT

Hi,

If you mean the modal dialogs, i agree with you that using additional user controls makes the program more complex. Maybe using directly ChildWindows is better approach ;). Thanks for advice

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

simple — Wed, 12 May 2010 17:08:36 GMT

This is way too much code. This is really over complicating things. Keep it simple.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

Balaji — Wed, 12 May 2010 07:57:27 GMT

Nice Article !!!!!

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

s. singh — Tue, 11 May 2010 18:46:27 GMT

Very nice. I've just started creating a bunch of SL4 ModalDialogs for a project..your article was timely.

RE: ModalDialogs, IEditableObject and MVVM in Silverlight 4

WPFDeveloper — Tue, 11 May 2010 14:04:22 GMT

Very nice article. Great work.