Prism is a framework for building loosely coupled, maintainable, and testable XAML applications in WPF, Windows 10 UWP, and Xamarin Forms.

New Prism Project - Use MEF or Unity?

I'm starting a new personal Prism 4 project. The Reference Implementation currently uses Unity.

I'd like to know if I should use MEF instead, or just keep to Unity.

I know a few discussions have mentioned that these two are different, and they do overlap, but will I be missing out if I simply choose Unity all the way?

Source: (StackOverflow)

What is Prism for WPF?

I've come across something called Prism a lot recently. Microsoft, who run the project, describe it as

Guidelines for composite applications in WPF and Silverlight.

Even after reading the more detailed descriptions out there, I have next to no clue what it's actually about, I'm afraid.

I'm hoping here that someone could give me a clear succinct explanation of what Prism actually is and why I should learn it. I have been a WPF developer for a couple of years now, used MVVM my fair share, and have lately encountered people using Prism, but personally feel a bit out of the loop here.

In particular, I'm wondering about the following points:

  • Is Prism literally just (or mainly) a booklet, as given on the MSDN site? Does it include any libraries, if so for what exactly?

  • Is Prism an MVVM framework? Should I be using it as the "official Microsoft MVVM framework" over others out there or my own?

  • Does it provide dependency injection? Does it relate to MEF at all in this way?

  • Anything else I should know about what Prism does, as a WPF/Silverlight developer.

Source: (StackOverflow)

WPF/Prism: What is a UNITY Container?

Can someone please explain to me the notion of a Unity Container like I'm a 6 year old kid? How does it work and what does it do?

Source: (StackOverflow)

WPF MVVM dialog example

Does anyone have any examples of showing a window dialog using MVVM (Prism)? - for example a configuration settings window when a command is executed.

All of the examples I've seen use the mediator pattern which is fine, but they also all have a reference to the view in the view model which is not ideal (we're using DataTemplates)


Source: (StackOverflow)

MVVM Light + Unity or Prism?

I am a little out-of-date in WPF right now and would be interested to hear peoples opinions on the latest version of Prism (which I used a couple of versions ago) vs an MVVM Light + Unity approach (which I have never done - decent examples URLs would be good).

My project will be a large one comprising multiple modules written by several developers. There is also the funds to bring in a 3rd party control suite in order to set up a nice workspace using one of the fancy Docking/Workspace layout managers out there (and I know some play better with the Prism regions than others).

If you were starting a project from scratch right now, what would you go with and why? Details on specific recommended architecture patterns would be useful (e.g. auto discovery of module dlls? Injecting logging service?). Basically, any thoughts and advice would be good. I'd like to get a good discussion going. Perhaps there is another direction entirely that you would suggest going in? I'm very much in the research phase and would like as much input as possible.

I put this on here because I thought it would get less biased points of view than the Prism/MVVM Light forums but, if there is a more suitable place for this question, please point me in that direction.

Source: (StackOverflow)

MVVM, Unity, Prism, MEF, Caliburn - What should I use?

Please help - I'm getting lost!

I'm writing a small desktop application which has some controls and some screen. This should later be integrated with a small web site, also having some screens. The idea is to let the user edit videos and select images, and then share their results with her friends.

The desktop app is using C# WPF, the web site - ASP.Net MVC.

I read that growing the application past a few screens would be easier using MVVM. So I started searching and discovered Caliburn.Micro and MVVM.Light. I have downloaded some tutorials but, just as I was getting ready to deep-dive into the material, I found here on S.O. that there's also Prism, MEF, Unity, ReactiveUI - This is becoming too much!

I'm terrible at learning new things - It's taking me ages to study WPF and ASP.Net MVC. I don't want to study lots of new material only to find out later that it's not relevant. And I don't have an architect to instruct me.

So my question is: Could you put these frameworks and technologies in perspective, and suggest which I should focus on studying and using (esp. what can be later used with Windows 8)?

Source: (StackOverflow)

Custom MVVM implementation Vs. PRISM

This question is inspired from this closed question:

What does Prism actually offer the developer? And is it worth it?

I have already implemented my own custom MVVM implementations in enterprise applications. I am interested in knowing:

  • Why should I learn PRISM (specifically PRISM, not other MVVM frameworks)?
  • Benefits of PRISM over custom MVVM implementation and
  • Is it worth the investment in learning PRISM?

I hope this question is not subjective and everyone please don't get into arguments :)

Source: (StackOverflow)

MVVM: Modified model, how to correctly update ViewModel and View?


Say I have a Person class, a PersonViewModel and a PersonView.

Updating properties from PersonView to the Person model is simple enough. PersonViewModel contains a Person object and has public properties the PersonView binds to in order to update the Person model.


Imagine the Person model can get updated by Service. Now the property change needs to be communicated to the PersonViewModel and then to the PersonView.

This is how I would fix it:

For each property on the Person model I would raise the PropertyChanged event. PersonViewModel subscribes to the PropertyChanged event of Person. PersonViewModel would then raise another PropertyChanged in order to update the PersonView.

This to me seems the most obvious way but I kind of want to throw this question out there in the hope of someone showing me a nicer way. Is it really this simple or are there better ways to mark the model as modified and update the respective properties on the ViewModel?


The PersonView's DataContext is PersonViewModel. Person gets populated from JSON and gets updated many times during its lifetime.

Feel free to suggest architectual changes for my particular case.


I marked aqwert as the answer of my question since it provided me with an alternative to the solution I already proposed.

Source: (StackOverflow)

Sync SelectedItems in a muliselect listbox with a collection in ViewModel

I have a multi-select listbox in a SL3 app using prism and I need a collection in my viewmodel that contains the currently selected items in the listbox.

The viewmodel doesn't know anything about the view so it does not have access to the listbox control. Also I need to be able to clear the selected items in the listbox from the viewmodel.

Not sure how to approach this problem

thanks Michael

Source: (StackOverflow)

MVVM: Binding to Model while keeping Model in sync with a server version

I've spent quite some time to try and find an elegant solution for the following challenge. I've been unable to find a solution that's more than a hack around the problem.

I've got a simple setup of a View, ViewModel and a Model. I will keep it very simple for the sake of explanation.

  • The Model has a single property called Title of type String.
  • The Model is the DataContext for the View.
  • The View has a TextBlock thats databound to Title on the Model.
  • The ViewModel has a method called Save() that will save the Model to a Server
  • The Server can push changes made to the Model

So far so good. Now there are two adjustments I need to make in order to keep the Model in sync with a Server. The type of server is not important. Just know that I need to call Save() in order to push the Model to the Server.

Adjustment 1:

  • The Model.Title property will need to call RaisePropertyChanged() in order to translate changes made to the Model by the Server to the View. This works nicely since the Model is the DataContext for the View

Not too bad.

Adjustment 2:

  • Next step is to call Save() to save changes made from the View to the Model on the Server. This is where I get stuck. I can handle the Model.PropertyChanged event on the ViewModel that calls Save() when the Model gets changed but this makes it echo changes made by the Server.

I'm looking for an elegant and logical solution and am willing to change my architecture if it makes sense.

Source: (StackOverflow)

prism vs mvvm light for wpf

We are starting a WPF with MVVM project and have to decide on PRISM or MVVM Light (I am new to both these frameworks). I have read through a few posts but still have a few questions. Can someone please throw some light on the following aspects w.r.t. both the frameworks?:

  1. Performance: Will either one framework perform better than the other for any reason?

  2. Communication within the app (viewmodel to viewmodel or between modules etc): I have read that MVVM Light has Messenging Service which appears to be fairly easy as well. But PRISM does not appear to have any equivalent. Is that true? How would PRISM handle interactions?

  3. Unit Testing: Have read that PRISM supports Unit Testing better. Can we still write NUNIT or VSTS tests in MVVM Light also?

Source: (StackOverflow)

How to do multiple shells in my Prism app (like MS Office)?

I try to create an application that has a window behaviour as MS Office, for example Word/Excel. The user opens the application and when clicking new, a completely new window shall appear with the look of the application.

The closest that I found so far is this: Link

However, here the shells are shown at application start. How to do this by command, or maybe there is a completely different way to achieve this?

Edit: I have also found the following now: Link, but where and how to call this code?

Source: (StackOverflow)

WPF Application fails on startup with TypeInitializationException

I have a simple WPF application which I am trying to start. I am following the Microsoft Patterns and Practices "Composite Application Guidance for WPF". I've followed their instructions however my WPF application fails immediately with a "TypeInitializationException".

The InnerException property reveals that "The type initializer for 'System.Windows.Navigation.BaseUriHelper' threw an exception."

Here is my app.xaml:

<Application x:Class="MyNamespace.App"

And here is my app.xaml.cs (exception thrown at "public App()"):

public partial class App : Application
    public App()
        Bootstrapper bootStrapper = new Bootstrapper();

I have set the "App" class as the startup object in the project.

What is going astray?

Source: (StackOverflow)

WPF-Prism CanExecute method not being called

I am coding a simple login UserControl with two TextBoxes (Username and Password) and a Login button. I want the Login button to be enabled only when the username and password fields are filled in. I am using Prism and MVVM. The LoginViewModel contains a property called LoginCommand that is bound to the Login button. I have a CanLoginExecute() method in my ViewModel but it fires only when the application comes up and then never again. So the Login button is never enabled. What am I missing?

Here's my xaml:

<TextBox x:Name="username"
    Text="{Binding Path=Username, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
<TextBox x:Name="password"
    Text="{Binding Path=Password, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
<Button Content="Login"
    cmnd:Click.Command="{Binding LoginCommand}" />

Here's my ViewModel

class LoginViewModel : IDataErrorInfo, INotifyPropertyChanged
    public LoginViewModel()
        this.LoginCommand =
            new DelegateCommand<object>(
                this.LoginExecute, this.CanLoginExecute);

    private Boolean CanLoginExecute(object dummyObject)
        return (string.IsNullOrEmpty(Username) ||
                string.IsNullOrEmpty(Password)) ? false : true;

    private void LoginExecute(object dummyObject)
        if (CheckCredentials(Username, Password))

    #region IDataErrorInfo Members

    public string Error
        get { throw new NotImplementedException(); }

    public string this[string columnName]
            string result = null;
            if (columnName == "Username")
                if (string.IsNullOrEmpty(Username))
                    result = "Please enter a username";
            else if (columnName == "Password")
                if (string.IsNullOrEmpty(Password))
                    result = "Please enter a password";
            return result;

    #endregion // IDataErrorInfo Members

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    void OnPropertyChanged(string propertyName)
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));

    #endregion // INotifyPropertyChanged Members

    #region Properties

    private String _username;
    public String Username
        get { return _username; }
            if (value == _username)
            _username = value;

    private String _password;
    public String Password
        get { return _password; }
            if (value == _password)
            _password = value;

    public ICommand LoginCommand { get; private set; }

    #endregion // Properties

Source: (StackOverflow)