patterns & practices: Prism

New Post: IRegionMemberLifetime

PeterForstmeier — Thu, 23 Feb 2012 06:58:07 GMT

Hi pedro,

you are right, the problem was the PartCreationPolicy.NonShared Attribute in View and ViewModel

I got it to work

Thanks for the help

Peter

New Post: Dynamic Views/Skins

MichaelDBang — Wed, 22 Feb 2012 23:37:39 GMT

Hello All,

I am currently attempting to create a mechanism whereby the user can select a particular skin for a Prism application. Currently this is done with a ContentControl at the Shell level, with bindings set as such:

<ContentControl Content="{Binding SelectedProfile.Content}" ContentTemplate="{Binding SelectedProfile.ContentTemplate}" />

I have a ComboBox which the user can drop down to select a different view profile.

The problem occurs upon the 2nd selection. The ViewProfile.Content for the initial ViewProfile and the second ViewProfile.Content both have controls with the same region name assigned via the attached property RegionManager.RegionName="regionname". When the 2nd ViewProfile.Content is set as the content to the Shell's ContentControl.Content property, the RegionManager.RegionName gets assigned a second time, but instead of simply attaching the control to the already-created region, it appears that Prism attempts to recreate the Region from scratch, resulting in a very ugly ArgumentException.

What is the best way of ensuring Regions are only created once and allow this scenario to work as expected? :)

Thank you,

Michael

New Post: Dynamic Views/Skins

MichaelDBang — Wed, 22 Feb 2012 23:37:39 GMT

Hello All,

<ContentControl Content="{Binding SelectedProfile.Content}" ContentTemplate="{Binding SelectedProfile.ContentTemplate}" />

I have a ComboBox which the user can drop down to select a different view profile.

What is the best way of ensuring Regions are only created once and allow this scenario to work as expected? :)

Thank you,

Michael

New Post: Need to Debug through SilverLight PRISM but can't

DCherubini — Wed, 22 Feb 2012 21:03:08 GMT

Hi,

Based on my understanding, as you copied the compiled Prism assemblies in the debug\bin folder of each project, your application seems to be using those assemblies instead of the Prism projects.

As far as I know, you should be able to replace the compiled Prism assemblies with their corresponding projects without problems. It would be helpful if you could provide us with more information regarding the error you are experiencing when trying to compile the Prism projects (for example, the classes or assemblies that are missing, the references of each project, etc).

Also, as a possible approach, you could try to replace the Prism assemblies with their corresponding projects in one of the several Quickstarts provided with Prism. If, after doing so, you cannot compile the Prism projects in the Quickstart, it would be helpful if you could provide us with the modified Quickstart in order to help you understanding what is preventing the Prism projects from being compiled.

Regards,

Damian Cherubini
http://blogs.southworks.net/dcherubini

New Post: Need to Debug through SilverLight PRISM but can't

DCherubini — Wed, 22 Feb 2012 21:03:08 GMT

Hi,

Based on my understanding, as you copied the compiled Prism assemblies in the debug\bin folder of each project, your application seems to be using those assemblies instead of the Prism projects.

Regards,

Damian Cherubini
http://blogs.southworks.net/dcherubini

New Post: Best practice to creating a new view and registering with a region

DCherubini — Wed, 22 Feb 2012 20:24:30 GMT

Hi,

Based on my understanding, the problem seems to be that you are trying to retrieve the context of a region in the view model before the construction of its view is finished. As the region is not available until the view is properly created, the region does not exist during the construction of the view model.

As a possible approach you could subscribe to the CollectionChanged event of the Regions collection of the RegionManager in the view model's constructor. When the ValidationGroupsRegion is added to the RegionManager this event will be fired and you should be able to retrieve the context of the region. For example, you could do something something similar to this:

[ImportingConstructor]
public ValidationGroupViewModel(IRegionManager regionManager)
{
    _regionManager = regionManager;
    _regionManager.Regions.CollectionChanged += Regions_CollectionChanged;
}

void Regions_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
    if (_regionManager.Regions.ContainsRegionWithName(RegionNames.ValidationGroupsRegion))
    {
        _regionManager.Regions.CollectionChanged -= Regions_CollectionChanged;
        var RegionContext = _regionManager.Regions[RegionNames.ValidationGroupsRegion].Context;
        this.Policy = RegionContext as PasswordPoliciesModel;
    }
}

However, take into account that the decision of which approach you should use will depend mostly of your personal preferences and the requirements of your scenario.

You can find more information about the RegionContext in the following section of the Prism documentation:

Chapter 7: Composing the User Interface - Sharing Data Between Multiple Regions

I hope you find this useful,

Damian Cherubini
http://blogs.southworks.net/dcherubini

New Post: Best practice to creating a new view and registering with a region

DCherubini — Wed, 22 Feb 2012 20:24:30 GMT

Hi,

[ImportingConstructor]
public ValidationGroupViewModel(IRegionManager regionManager)
{
    _regionManager = regionManager;
    _regionManager.Regions.CollectionChanged += Regions_CollectionChanged;
}

void Regions_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
    if (_regionManager.Regions.ContainsRegionWithName(RegionNames.ValidationGroupsRegion))
    {
        _regionManager.Regions.CollectionChanged -= Regions_CollectionChanged;
        var RegionContext = _regionManager.Regions[RegionNames.ValidationGroupsRegion].Context;
        this.Policy = RegionContext as PasswordPoliciesModel;
    }
}

However, take into account that the decision of which approach you should use will depend mostly of your personal preferences and the requirements of your scenario.

You can find more information about the RegionContext in the following section of the Prism documentation:

Chapter 7: Composing the User Interface - Sharing Data Between Multiple Regions

I hope you find this useful,

Damian Cherubini
http://blogs.southworks.net/dcherubini

New Post: IRegionMemberLifetime

Pedro_C — Wed, 22 Feb 2012 19:54:36 GMT

I think you will also need PartCreationPolicy.NonShared on your views. I also think you need to return false in IsNavigationTarget. As far as I understand, if you return true you are saying the existing viewmodel instance can deal with the navigation request. If you return false, a new viewmodel/view should get created and the old one should then get disposed.

There is a useful diagram showing the navigation flow here: http://msdn.microsoft.com/en-us/library/gg430861(v=pandp.40).aspx

Hope this helps - I've been through the pain!

Reviewed: Prism 4 - November 2010 (Feb 22, 2012)

tdracz — Wed, 22 Feb 2012 16:29:52 GMT

Rated 2 Stars (out of 5) - It seems that 4.1 release still has references to SL 4 libraries, which causes the following errors in Code Analysis: The indirectly-referenced Silverlight assembly 'mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' could not be found(...) This assembly was referenced by: (...)Microsoft.Practices.Prism.dll.

Reviewed: Prism 4 - November 2010 (Feb 22, 2012)

tdracz — Wed, 22 Feb 2012 16:28:06 GMT

New Post: SL5 InteractionRequestTrigger

ltheONEl — Wed, 22 Feb 2012 12:16:29 GMT

I found that by inalling Expression Blend preview for silverlight 5 solved the issue. It ships with the dlls versions required.

New Post: SL5 InteractionRequestTrigger

ltheONEl — Wed, 22 Feb 2012 12:16:29 GMT

I found that by inalling Expression Blend preview for silverlight 5 solved the issue. It ships with the dlls versions required.

New Post: IRegionMemberLifetime

PeterForstmeier — Wed, 22 Feb 2012 10:18:26 GMT

Hi Pedro,

i'm using MEF.

The Exports of my ViewModels are definied as follows:

 [Export(typeof(IUserControl2ViewModel))]

 [PartCreationPolicy(CreationPolicy.NonShared)]
 public class UserControl2ViewModel : IUserControl2ViewModel, INavigationAware,IRegionMemberLifetime
 {

 
public bool IsNavigationTarget(NavigationContext navigationContext)
        {
            logger.Log(String.Format("Model2 - IsNavigationTarget <{0}>", navigationContext.Uri), Category.Info, Priority.Low);
            return true;
        }
 public bool KeepAlive
        {
            get
            {
                logger.Log("Model2 - KeepAlive",Category.Info, Priority.Low);
                return false;
            }
        }
/// <summary>
/// Interaction logic for UserControl1.xaml
/// </summary>
[Export("UserControl1")]
public partial class UserControl1 : UserControl
{

.......
}

The Constructor UserControlXY and UserControlXYViewmodel are called only once when i'm navigation to the View/Model the first time,

for all usages of the Views/ViewModels there is no more Constructor call.

Peter

Updated Wiki: Home

brumfb — Tue, 21 Feb 2012 21:01:02 GMT

Welcome to the Prism Community

Overview

Prism provides guidance designed to help you more easily design and build rich, flexible, and easy-to-maintain Windows Presentation Foundation (WPF) desktop applications, Silverlight Rich Internet Applications (RIAs), and Windows Phone 7 applications. Using design patterns that embody important architectural design principles, such as separation of concerns and loose coupling, Prism helps you to design and build applications using loosely coupled components that can evolve independently but that can be easily and seamlessly integrated into the overall application. These types of applications are known as composite applications.

Prism includes reference implementations, QuickStarts, reusable library code (the Prism Library), and extensive documentation. This version of Prism targets the Microsoft .NET Framework 4.0 and Silverlight 4 and includes new guidance around the Model-View-ViewModel (MVVM) pattern, navigation, and the Managed Extensibility Framework (MEF). Because Prism is built on the .NET Framework 4.0 (which includes WPF) and Silverlight 4, familiarity with these technologies is useful for evaluating and adopting Prism.

Intended Audience

Prism is intended for software developers building WPF or Silverlight applications that typically feature multiple screens, rich user interaction and data visualization, and that embody significant presentation and business logic. These applications typically interact with a number of back-end systems and services and, using a layered architecture, may be physically deployed across multiple tiers. It is expected that the application will evolve significantly over its lifetime in response to new requirements and business opportunities. In short, these applications are "built to last" and "built for change." Applications that do not demand these characteristics may not benefit from using Prism.

It should be noted that while Prism is not difficult to learn, developers must be ready and willing to embrace patterns and practices that may be new to them. Management understanding and commitment is crucial, and the project deadline must accommodate an investment of time up front for learning these patterns and practices.

Getting Started

Prism 4.1 Download for WPF 4.0, Silverlight 5, and Windows Phone 7.1
Prism 4 Download for WPF 4.0, Silverlight 4, Windows Phone 7.0
Visual Basic Prism 4 Reference Implementations, QuickStarts, and Hands-on Labs
Prism 4 Readme
Developer's Guide to Microsoft Prism (Version 4.1 and 4.0 on MSDN)
What's new in Prism 4
Prism 4 Documentation (includes a PDF format)
Prism (all versions) Knowledge base
Prism (all versions) Known Issues

Additional Links

Windows Phone 7 Developer Guide is under development. Download it here .
The ManifestManagerUtility for ClickOnce deployment can be found here.
Project Linker on Visual Studio Gallery here.
MVVM Training here.
The patterns & practices roadmap can be found here.

Previous Releases

Prism 2.1 targetting Visual Studio 2008, WPF and Silverlight 3, named Composite Application Guidance can be downloaded on MSDN here.
To learn about upgrading from previous versions of Prism, go here.

Future Releases

Prism 4.1 targetting Silverlight 5. Go here to learn about future releases.
Prism 4.5 targetting .NET 4.5.

New Post: IRegionMemberLifetime

Pedro_C — Tue, 21 Feb 2012 16:12:32 GMT

Peter, are you using Unity or MEF? If using MEF, what PartCreationPolicy attributes are you using on your View and ViewModel? I think you need to use CreationPolicy.NonShared. Also, are you using RequestNavigate to navigate to your views or are you using RegisterViewWithRegion. If using RequestNavigate, what code do you have in IsNavigationTarget?

New Post: How to stop Navigate when error raised?

Cuiqs — Tue, 21 Feb 2012 14:29:12 GMT

I want to Check authorization before load the view. if no authorization, the view will not show.

I use below code, it just show error message, but not to stop show the view

NavbarViewModel:

  private void NavItemDoubleClick(object navItem)

        {
            if (navItem == null) return;
            NavMainMenuInfo item = navItem as NavMainMenuInfo;
            if (string.IsNullOrEmpty(item.ViewName))
                return;
           
            this.regionManager.RequestNavigate(RegionNames.DocumentRegion, new Uri(item.ViewName, UriKind.Relative),

NavigationCompleted

);
                    
        }
         
    
        private void NavigationCompleted(NavigationResult result)
        {
            if (result.Error != null)
                MessageBox.Show(Error.Message);
            
            IsBusy = false;
            
        }

UnitViewModel:

    public void OnNavigatedTo(NavigationContext navigationContext)
        {
            if(!(Csla.Rules.BusinessRules.HasPermission(Csla.Rules.AuthorizationActions.GetObject, typeof(Unit))))
                throw new Exception("...");

            if (this.Model == null)
            {
                IsBusy = true;
                BeginRefresh(callback => UnitList.GetAll(callback));
            }
        }

New Post: How to stop Navigate when error raised?

Cuiqs — Tue, 21 Feb 2012 14:29:12 GMT

I want to Check authorization before load the view. if no authorization, the view will not show.

I use below code, it just show error message, but not to stop show the view

NavbarViewModel:

  private void NavItemDoubleClick(object navItem)

        {
            if (navItem == null) return;
            NavMainMenuInfo item = navItem as NavMainMenuInfo;
            if (string.IsNullOrEmpty(item.ViewName))
                return;
           
            this.regionManager.RequestNavigate(RegionNames.DocumentRegion, new Uri(item.ViewName, UriKind.Relative),

NavigationCompleted

);
                    
        }
         
    
        private void NavigationCompleted(NavigationResult result)
        {
            if (result.Error != null)
                MessageBox.Show(Error.Message);
            
            IsBusy = false;
            
        }

UnitViewModel:

    public void OnNavigatedTo(NavigationContext navigationContext)
        {
            if(!(Csla.Rules.BusinessRules.HasPermission(Csla.Rules.AuthorizationActions.GetObject, typeof(Unit))))
                throw new Exception("...");

            if (this.Model == null)
            {
                IsBusy = true;
                BeginRefresh(callback => UnitList.GetAll(callback));
            }
        }

New Post: Prism/WPF/Navigation issue

ramanujam1970 — Tue, 21 Feb 2012 05:04:33 GMT

I'm having touble firing up IConfirmNavigation Request. ViewModel implements IConfirmNavigationRequest Following methods are implemented to satisfy above interface.

ConfirmNavigationRequest,

IsNavigationTarget,

OnNavigatedFrom

OnNavigatedTo

I'm using WPF/MEF container. Also I'm using TabControl(as in stocktrader RI) which when clicked on one of the menu item will hydrate a view. I want Navigation event to fire so that I can have save logic there. Any help appreciated. I went some similar post , but not working.Any help appreciated.

New Post: Prism/WPF/Navigation issue

ramanujam1970 — Tue, 21 Feb 2012 05:04:33 GMT

I'm having touble firing up IConfirmNavigation Request. ViewModel implements IConfirmNavigationRequest Following methods are implemented to satisfy above interface.

ConfirmNavigationRequest,

IsNavigationTarget,

OnNavigatedFrom

OnNavigatedTo

New Post: ViewModelLocator

jfraschilla — Tue, 21 Feb 2012 03:45:13 GMT

Being new to WPF and Prism I wanted to get some advice on the best way to implement ModelViewLocator in order to get blendability. Currently I am converting a WinForms application to WPF using Prism and have the basic skeleton of the application completed. My application has four regions, treeViewRegion (for selecting a view), mainRegion (where the view gets injected), a menuBarRegion, and a ToolBarRegion. Each mainView inserts itself into the list in the treeviewRegion and also inserts it’s own menuView and toolBarView into the appropriate regions. I started to learn Blend so I wanted to know if there is a way to see all regions in design mode. I was reading about MEFedMVVM, MVVMLight, ViewModelSupport by Brian Fenisio, and a number of blendability articles by Tomer Shamam. I want to know what the best path to implement this is and if I will be able to see all regions during design time.