Friday, October 17, 2014

PopUps with Interactivity

Just about every application has a need to notify user about an event or ask for confirmation before proceeding onto the next operation. Prior to MVVM, we would have used the MessageBox class in the code-behind. But for MVVM applications, that’s not the appropriate way as it breaks the separation of concerns from the view or viewmodel. There are lots of ways to show popups in MVVM application. In Prism, we just happen to use triggers.

Triggers are used to initiate actions when a specific event is raised. So, it means we have to setup a view to detect the interaction request of event and then present an appropriate visual display for that request.

What is required for raising events?
Now for raising events, we need an event trigger. But not just any event trigger. We don’t want to use the built-in event trigger, instead Prism provide its own InteractionRequestTrigger. This trigger binds to the source object or the InteractionRequest object that exist in your viewmodel. It automatically wires up and connects to the appropriate raised event on that request.

What next?
Once that request event is raised, the InteractionRequest should than invoke an action and this action call the PopUpWindowAction and displays a popup window to the user. When it is shown its data context is set to the context parameter of the InteractionRequest.

You can even specify your own custom window content by setting the window content property on the popup window action object. The Tile of the popup window is bind to the Tile property of the context object

There is couple of interfaces one need to know about:
1)      INotification
2)      IConfirmation
3)      Custom

INotification has two contracts on its two properties as Tile and Content. The Tile property, I just talked about is the property it reads from. Next is the Content property, which is going to be our message. So, if you are not providing your own window content, this message is what’s going to show in the default popup window, that is shown using this request. I like to mention that INotification request is only used when you are trying to notify user about something.

Next we have is IConfirmation request, which extends INotification. It adds a new confirmed property which basically signifies, if the request was confirmed or not. We use IConfirmation request for scenarios where we want to use a messagebox for Yes/No type answer.

And of course you can always create your custom request. So, if you want to pass custom objects or custom information or INotification - IConfirmation doesn’t solve your problem, you can create your own.
Implementing Popups
Implementing popups are not at all difficult whilst below steps are followed:
1)      Declare InteractionObject<T> object in viewmodel
2)      Need a DelegateCommand to raise request
3)      Add trigger in view
4)      Inside trigger, add InteractionRequestTrigger
5)      Add PopupWindowAction
6)      Bind command to button

Code starts here...
Let's create a simple view with a button and a label. On click of this button, we will see how to show notifications using MVVM and my label will display the status of notification.

I have a viewModel which has a single property called Status and this property will be used to display response of my request. 

Before moving further, let's go ahead and add reference of Prism.Interactivity using Nuget. Once reference is in place, we will quickly modify our viewModel by adding property of type InteractionRequest<T>. Here T is the type of request, we want to use which is INotification in our case:

 public InteractionRequest<INotification> NotificationRequest { get; set; }

Now for every getter/setter we should have a corresponding command, which will help us in invoking this request:

public ICommand NotificationCommand { get; set; }

Next thing is to instantiate above properties in our constructor of viewModel and raising the notification as:

In above snippet, you will notice that I also provided callback. This callback will get executed, when user acknowledges the notification and dialog closes. In my case, I am setting my Status property to 'Done' in callback.

Now, rest of work is in our view. In order to support notifications, couple of namespaces need to be added in view for Interactivity and Prism.
Next we need to add some interaction triggers:
        <prism:InteractionRequestTrigger SourceObject="">
            // TODO: Define action here

In above snippet, we need to set SourceObject. In our case, SourceObject is the request object, which is set in our viewModel and we call it NotificationRequest.
Once SourceObject is set, we need to define an action. For us, it will be PopupWindowAction. Next thing is invoking the request, which will fire our trigger and will in turn show our popup window. In order to achieve that, we need to set a command property on our button. Once all above things are done, our code will look like:

We are all set. Quickly build and run your solution. You will land up with below screen:

Click on the PopUp button, you will receive a notification message as:

As soon as user clicks on OK button, label on the MainWindow will get updated as:

User is notified. So, our callback successfully updated our status property. Hope you enjoyed learning !!!

Saturday, October 4, 2014

Introducing Windows 10

Hope most of you are aware that in the mid of last week, Microsoft announced Windows 10 (Technical Preview). This preview is a small set of new code and is not the final one. It means lot more is on the way :)

This release contains desktop-focused features, primarily for business customers. Actual consumer preview is plan to launch somewhere around January.

Windows 10 will run across unbelievably broad set of devices from 4 inch screens to 80 inch screens. Some of the devices we can hold in hand and others are 10 feet away.
So, are you ready to dive into the new features?
Well, let's start.

Start Menu: Start menu with Live tiles and favourite apps

Everything runs in a window: Windows store apps now opens in the same fashion as desktop apps format – can be re-sized and move around – have title bars

Snap Enhancements: New quadrant layout to view four snapped apps in single shot

Multiple Desktops: Creation and switching between multiple desktops

Find files faster: Feature to list out recently used files in File Explorer

Sometimes, trying out such an early build can be risky. So, it is always recommended to read the precautionary notes before proceeding for installation on a primary/business machine.
Once Windows Technical Preview is installed, recovery partition won’t work. It means, if you want to go back to your previous version of Windows, then you have to re-install that version from the installation media. More...

Wednesday, September 17, 2014

What's New In Prism 5.0?

Are you WPF, Silverlight or Windows Phone developer and used Microsoft’s patterns and practices library to build your applications? If you are, then you might want to know that Microsoft’s patterns and practices team have just released Prism 5.0. All the applications built using the previous versions of Prism are now broken. So, in this artifact, I’ll be discussing about the new assemblies, new objects and deprecated objects which can/can’t be used with Prism 4.1 and Prism 5.0.
Downloading Prism 5.0

Prism 5.0 can be downloaded and installed either from patterns and practices site having URL as or by using Nuget package inside Visual Studio. Mentioned link also discusses about all the changes which are part of Prism 5.0

Supported Platforms
Let’s have a quick look at the supported platforms of Prism 5.0. While working with previous versions of Prism (i.e. 4.1), one was able to create applications like WPF (.Net 4.0), Silverlight 5 and Windows Phone (7.5). Point to note here is, Prism 5.0 only supports WPF (.Net 4.5).

Prism 4.1
Prism 5.0
WPF (.Net 4.0)
WPF(.Net 4.5)
Silverlight 5
Windows Phone (7.5)

In other words, if your application is written in Silverlight or Windows Phone and you are planning to upgrade to Prism 5.0, then it’s not going to work. In this case, either you have to use some tool and make your application as WPF application (if possible) or simply stick to the existing version of Prism.
Assembly Changes

This section discusses about all the assembly related changes that Prism 5.0 introduces. Please note, in below table all the assemblies are prefixed with Microsoft.Practices:

Prism 4.1
Prism 5.0
Prism.Composition [Renamed]
Prism.Interactivity [No change here]
ServiceLocation [No change here]
Unity [It is now a PCL]
Prism.SharedInterfaces [Is is also a PCL]
Prism.MVVM [It is also a PCL]
Prism.PubSubEvents [It is also a PCL]

If you will see above table, the assembly named Microsoft.Practices.Prism in Prism 4.1 is no longer called Microsoft.Practices.Prism in Prism 5.0. Now this assembly is renamed to Prism.Composition.
There is no change in Prism.Interactivity, ServiceLocation, Prism.UnityExtensions and Prism.MefExtensions front.

This Prism.Composition takes dependency on another new assembly called Prism.SharedInterfaces, which is a PCL (Portable Class Library).
On MVVM front, there are two more additions. One is Prism.MVVM which is again a PCL and shares a common MVVM functionality across Windows Store Apps and Windows Presentation Foundation applications. Now to get around of few limitations and some needed enhancements on WPF, a separate assembly is created having name as Prism.MVVM.Desktop, which is specifically meant to be used on desktop.

One more addition is Prism.PubSubEvents. This is event aggregator. So, event aggregator is called out of Prism and has been kept into its own PCL library in Prism 5.0

Deprecated Objects
Deprecated objects are the objects which are still in assemblies but we just don’t want to use them anymore and if you are currently using them, then you have to move them to different object instance. Below is the list of such objects:




Microsoft.Practices.Prism.MVVM.BindableBase class




Microsoft.Practices.Prism.MVVM.PropertySupport class




Microsoft.Practices.Prism.PubSubEvents.PubSubEvent class



Objects moved to new location

There are few objects which are given the new home in Prism 5.0. If you are using any of the below mentioned objects, then you have to re-reference your assemblies with the new ones. Apart from assemblies, namespace is also changed. Please note, below mentioned changes are the breaking changes.

New Location

Removed Objects
There are few objects in Prism 4.1, which are completely removed from Prism 5.0. This section discusses about the objects that are completely gone. This is again considered as a breaking change.

ButtonBaseClickCommandBehavior Click
Marked as obsolete in Prism 4.1

Apart from all these changes, few changes are made to Quick Starts and help files also.

Wednesday, June 4, 2014

First CTP of Visual Studio "14"

Yeah you heard it correct, Visual Studio "14" is on the way and most likely it will be available by 2015. This will include few major updates of Roslyn with better refactoring support, new ASP.Net templates for vNext, new features of C++ 11 and much more. List of known issues with Visual Studio "14" and download details can be found here.

So, get ready for something new again :)

Thursday, May 29, 2014

Propagating Property Change for Static Properties

While working on any XAML based app, first thing which comes into mind is Binding. There are lot many articles on what is Binding and how it works. Don’t worry, I am not going to repeat all that stuff again. But definitely, I would like to touch upon few things which are base of my today’s write-up.

To make any property bindable or let’s say to propagate property change, we usually follow one of the below two options:
  • Implement INotifyPropertyChanged interface or
  • Create an event with name PropertyNameChanged

Point to notice here is, both the above options will work only on instance properties. Now what if my property is Static???

INotifyPropertyChanged is not going to work for static properties. None of the above options will make x:Static extension work.

What to do now ?

No worries, all these hazards can easily be overcome when you will jump to .Net 4.5.

Approach 1: Property specific static event for each and every static property
Let’s have a look at the below code:

Analysing Approach 1: Given approach will be feasible only when we have 1 or 2 static properties. If there are many static properties, then code will be bulky and un-maintainable as each property will have separate event.

Solution: Instead of writing static event for each and every static property, one generic event should be there.

Approach 2: Single Generic static event for all the static properties
Let’s have a look at the below code:

Analysing Approach 2: This approach will work very smoothly irrespective of how many static properties are present in a given class.

Point worth mentioning about EventHandler parameters:

Why null is passed as a parameter in EventHandler?
First placeholder is for passing instance. But as this is Static property, instance value will be null. 

Hope you enjoyed learning this new feature.

Tuesday, May 27, 2014

Identify WPF version

If you want to figure out the current version of WPF installed on your machine, then one has to navigate to registry for below path:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.0\Setup\Windows Presentation Foundation

Version value on above path will give your the required information.

Monday, May 12, 2014

.Net Framework 4.5.2 is available

Microsoft recently released .Net Fx 4.5.2 which is in-place update for .Net Framework 4, .Net Framework 4.5 and .Net Framework 4.5.1 and is ready for download on below links:

This includes updates for ASP.Net, Windows Event Tracing (ETW), better profiling as well as for DPI settings. Enjoy...