I'm beginning modelling an existing application for controlling a cash collection terminal. I'm very new to the Prism / Composite Application Library and would like some advice on how I could begin modelling this application using the Prism library.
Basically the application manages a cash terminal that accepts frequent cash drops, counts notes in the deposits, communicates via a 3G/Edge connection with our central server to replicate deposit and other data, and performs cashups. Central to all this is management of the cash canister. The application is not UI intensive, but we are moving away from WinForms to WPF, and I am supposed to use this framework for all future development.
At its most fundamental core, Prism is an application composition framework. It allows you to modularize your application. The thing to start thinking about it what parts of your application need to be modular.
A module is a unit of functionality that is useful on its own, but doesn't make the application useless if it is replaced or removed. For example, in an application I've written for work we have two different types of contacts for which we handle cases. We have a module for each contact type that contributes functionality specific to that contact type. The application is still usable without one or the other and in this way we can work on or test each component individually as well as together.
Hopefully this gives you a guide to how to model your application. Prism seems complicated, but it helps to understand that what you really get with Prism is this ability to slice up your application. From a high level, this is what you'd probably be more interested in modeling.
Related
I'm starting to jump in to WP7 development and I have a few questions. My current background/experience is with ASP.NET. I'm new to Silverlight as a whole, so I have some questions regarding the architectural design of the application. I don't have experience with MVC, and it appears that Silverlight is based off of it. Is that true? To my original question:
Once the new developer tools come out, the app will have a SQL CE back end that, as a future release, will sync with SQL Azure. I'd also like to provide a web based application that performs the same functions, and interacts with the Azure database. I'm wondering how I should structure the app to minimize any code duplication.
I was thinking of using a generic n-tier architecture. UI > Business Layer > DAL (LinqToSql) > Sql. These classes could get re-used on the web too.
Silverlight is not really based on MVC. In fact, you can implement any architectural pattern as long as you fully understand its functionality. Most people prefer MVVM, which is similar to MVC, the only main difference is that the controller is replaced by the ViewModel that plays the role of an intermediary data link between the model and the view.
With the release of Mango, you will indeed have access to SQLCE. In your case, since you are planning on using specific interoperability layers, I would recommend building both applications in Silverlight with an intermediary web service that will communicate with the data storage (in your case it will be Azure). You win in two points:
You are using Silverlight, which means that you can use a similar codebase (with platform adjustments, of course) to deliver the same functionality.
The web service is app-independent. Therefore if you ever decide to build, let's say, an iOS application, you will be able to use the same communication layer without major changes.
There seems to have a buzz around the Lightswitch application framework.
Reading some posts/forums/articles and listening to a video provdided some answers, but raised some others.
Extensibility?
Is there several hooks to override or extend features?
Modularity? Can MEF/Prism be integrated? Is there a concept of dynamic modules that can be loaded at runtime?
Localizable? Any special features about localization in different languages?
Versionnable? Any concept of version so simultaneous version can co-exist?
Abstraction? The connection to data source can be abstracted and replaced?
Testability? Are the different components unit testable in an automated way? Easy or difficult to achieve?
Cross-cutting / NFR ? Any hooks so we can plug NFR code? (logging, caching, audit, secuity )
Is this a solid framework to build some PAAS application over?
Let me give you my 2 cents based on an eval I just did:
Extensibility
You can of course add custom controls and apparently there will be a published extensability API.
Modularity
No. Lightswitch is not a code generator, it abstracts out implementation of the UI.
Localizable
Did not see anything, but I imagine this will occur in stages.
Versionnable?
You could TFS the Lightswitch project, but if you mean versioning from an execution standpoint ... it's as simple as deploying a new version of the app to the server. The client will check for updates on run and install as necessary from what I understand.
Abstraction
Yes, if you abstract it at the WCF RIA Services layer which is very easy to do.
Testability
Business rules can be implemented at the RIA Services layer so testing there should be a snap, but if you rely heavily on rules driven through the UI you will have to use another UI-based testing tool.
Cross-cutting / NFR
If you focus on getting the RIA Services tier of the app to be the central location for business rules and let the UI just focus on user experience you won't run into much overlap. I think Lightswitch is a good client for many solutions, but the core power of it is using it as a client for RIA Services which itself is not dependent on Lightswitch by any stretch.
I hope I at least provided some useful insight.
Extensibility? When the built-in LS controls don't allow you to do what you need, you can use just about any Silverlight control (including 3rd party controls), or create your own custom Silverlight controls. There is a little more work to do than using LS controls, because the LS controls have some extra "smarts" built into them, so you can just drop them on a screen, bind, & use them. There are also extensibility points built into the framework that allows you to create your own "extensions" (shells, controls, themes etc).
Modularity? LS already uses MEF under the covers, so it's quite possible that it may be able to be leveraged further in the future. LS does generate code, but for itself, not for external consumption. There is an excellent article, however, by Microsoft's Eric Erhardt
http://blogs.msdn.com/b/lightswitch/archive/2011/04/08/how-do-i-display-a-chart-built-on-aggregated-data-eric-erhardt.aspx
that shows how to reuse the data model that LS constructs (in Eric's case, he uses it to create a RIA service that aggregates data for presentation in a chart control).
Localizable? I don't believe there are currently any built-in localisation features.
Versionable? For a web-based app, if the data schema didn't change, I don't see why you couldn't publish separate versions, but desktop (OOB) apps are click-once apps & are therefore governed by that technology.
Abstraction? If you were to create a RIA service for your data source, you could abstract away the implementation details.
Testability? Unfortunately, V1 was not written with "testability" in mind. If you extract out your business logic into Silverlight class libraries (for use on the client, or full .NET class libraries for use on the server), you can unit test that logic, but the code that you write in an LS application itself is not really unit-testable at this point in time.
I am developing a silverlight application for the past 6 months using prism framework. When I look at the code base now it has grown huge with lots of modules, event aggregators, inter module communication code etc. On hindsight I am contemplating whether I made the right choice. Is there any other simpler framework I should have gone for ?
Prism is at its best when targeting a large application. Why? Because the core concepts Prism provides, such as Modularity, UI Composition, support for MVVM, etc. are used the most in this kind of applications.
The idea, as you said, is that you are likely to end up with a bunch of modules. The benefit of that is that your application is decoupled, and modules can be tested in absolute isolation so they are easy to maintain.
By using Prism, or any other library/framework that modularizes your application, (correctly) in large applications, you don't need to go through your entire application looking for bugs when you make a change to one of the parts. This is not true in monolithic applications, where making a minor change might bring down the entire app.
Another plus for Prism in this scenarios is that it allows multiple teams to work on different modules simultaneously, without affecting each other's work. This is specially useful when working with distributed teams.
The thing that would convince you of making the right choice, would be comparing the application you created with the same one but with high coupling of its components.
I hope this helps
I'm considering using Silverlight for a business type application which will contain probably a dozen or so screens. The screens will contain data entry forms with edit fields, grids, lookups, calendars, etc. Typical business application type screens. I want this to run in the browser but don't want to mess with HTML, JavaScript, CSS etc. Is Silverlight 3 appropriate for this type of application? Can someone build professional level business type apps with Silverlight 3?
#Randy Minder,
Glad to hear that you want to use silverlight 3 for line of business application.
I used to develop line of business applications in ASP.NET combined with javascript/AJAX. I am currently developing my first silverlight 3 line of business application and found silverlight is better in few departments. The following are the Pro/Cons observed by me PERSONALLY.
Pros
Layout/Styling(CSS)
XAML + silverlight 3 styling is very flexible and less cluttered when compared to CSS. I am not a designer and I hate having to deal with CSS. But in the case of silverlight, I really enjoyed creating the mockup,layout & styling. The end result is awesome. This is the first application that I developed has decent & consistent look & feel. I hope you will also find silverlight xaml to be easier to deal with.
Rich Interaction & Language support
I used to use Ajax, javascript for creating rich interaction experiences like populating some data dynamically when user interacts with UI. Writing some complex UI logic in Javascript is daunting. Though there are some nice javascript libraries like Jquery, I think writing UI complex logic in C#/VB.NET/F# is much easier than to write it in javascript. Dealing with rich interactive controls in silverlight is much easier than with javascript/ ajax controls. Writing server communication code with WCF or WCF RIA service is far easier than with ajax calls.
Browser compatibility
Each browser is different from another in one or the other way, like some browser supports something and others dont. Having to deal with browser differences in javascript is also a pain. Silverlight being a plugin doesn't have to deal with browser differences. No problems dealing with layout engine differences too.
Animations/multimedia
Ofcourse with line of business applications we will not use toooo much of animations/multimedia. However we can use small animations like menu popup, sliding controls, fading transitions for when data changes etc. These are very easy to implement in silverlight than with asp.net/javascript
Validation
Validation support in silverlight is awesome you can write more validation logic in less time.
Popup messages
Popup messages are very clumsy to deal in ASP.NET and sometimes I need to store some information in hidden fields to feed text for popup messages. Hidden fields are used as javascript & ASP.NET interaction components which are difficult to maintain and end up with more code.
Good separation of presentation & model
Though you can separate these layers in ASP.NET also, silverlight enforces this by design which is good. In my team there are few developers who dont want to put effort on separation of the layers. Unfortunately they are the seniors in age and decision makers. I always hate to deal with their spaghetti code. Not to say that I am a better developer than them, I always put some effort to separate the concerns and try to learn how to manage my code. ASP.NET webforms doesnt enforce separation of presentation & model by design. Where as silverlight enforces this by design and my life became easier.
Cons
Clipboard
Users are very much used to copy the content available on ASP.NET/HTML page. Most of the silverlight 3 controls doesnt support clipboard out of the box. The only control I know that supports out of the box is textbox.
Database Communication
Database communication in ASP.NET is easier & direct communication is possible. However silverlight being client side technology it doesnt have direct access to database and a necessity of creating an additional tier is mandatory. Though WCF RIA services make the development of this additional tier easier, still WCF RIA services is in beta as of now. Though I am mentioning it as disadvantage, I did not really feel it is as REAL disadvantage because creating a WCF service is not that difficult.
Client side resource usage
Though cost of hardware reduced alot,client side hardware resources are not unlimited when compared to server side. At my work place, though PC provided have decent configuration, most of the users open lot of applications simultaneously which is required to accomplish their day to day tasks. Silverlight uses client side CPU/memory. Some of my users are complaining that the application I developed is using more CPU/memory than the asp.net equivalent. So if your users have slower PCs, consider ASP.NET or design your silverlight application more carefully.
One may say installing silverlight plugin as disadvantage, I did not face the problem because my application is a intranet application and all users installed silverlight with a single email request.
These are MY experiences with silverlight 3. The only major issue I faced was clipboard support in silverlight, I hope MSFT will address this soon.
All in all, silverlight ROCKS!!! Silverlight 3 is ready for enterprise and if you can wait for few more months Silverlight 4 will be released which has even better support for line of business applications. I dont want to develop ASP.NET applications anymore, that doesnt mean that I will quit using ASP.NET, I will use it only when necessary. I fell in love with silverlight and for a good reason. Designing part of the website is the one I used to hate most but with silverlight designing became one of my favorites.
I hope that silverlight 3 will help you in your decision making.
Absolutely. Take a look at this post about the Vancouver Olympics:
http://csharperimage.jeremylikness.com/2010/02/vancouver-olympics-howd-we-do-that.html
That's just one example of a business application in the "real world" being used to drive a massively complex operation. I posted that just to draw attention to the "business" side of Silverlight, but be sure to click the link to the original post to see the other partners and contributions to the project.
I've been building enterprise/business applications with Silverlight for over a year now. So the answer is an emphatic "Yes, you can" and "Yes, it's been done" and "Yes, it's been done on a large scale with large companies, and very successfully."
I agree #Jeremy. Make sure to use RIA Services with Silverlight , You will get a very manageable/maintainable application. Even one more benefit is that you can make the SL app Out of browser too.
We are developing/mantaining an enterprise application which for historical reasons and development speedup it was targered for WinForms.
Now we are thinking that sooner or later (more sooner than later) that application will need to be Web based.
Thinking on the "to-Web" movement. Which are the most important things we have to consider? Something like, thing on MVP parading (or others), determine now the kind of platform/framework you are going to use, ...
Any experience on migration from winforms to web? Any suggestion to take care?
Aclaration: In our scenario the application would be nice NOW to be Web based but we are realistics. I agree that not all the applications have to be Web based (this is the main reason we developed with WinForms!). But sometimes the requirements changes and, in our scenario, we want to offer that application as SaaS.
The main thing is to completely separate the user interface from everything else. Once you've done that, you won't be rewriting the application in order to port it - you'll just be creating a web UI on top.
NESBAWA (Not Everything Should Be A Web App).
I worked for a company that went through a similar situation with their monolithic WinForms application. From that experience, there are two things to consider:
1] Decouple all data access logic (DAL) from the existing WinForms UI. You can start this process before any web development begins.
We did this refactoring in a series of 6 weekly sprints. Some parts of the app were easy to change - others were made of completely hellish spaghetti code that interwove DAL, inline SQL and UI code all in the code behind of the WinForm.
Once you have this separation in place, supporting two different UIs is easier.
2] Ignore ASP.Net MVC and target WebForms. WebForms was designed to make writing a web application close to the experience of writing traditional WinForms UI code (event driven, component based).
You need to understand the page lifecycle, and there are a few conceptual gotchas around dynamically generated controls that tend to trip up a lot of newcomers - but otherwise it's the most painless way to get a team of WinForms developers doing web stuff. MVC maybe very popular in web circles right now, and it provides a better separation of concerns (though you can achieve similar results with WebForms with a bit if diligence and strong design leadership) - but it requires a higher degree of knowledge. With MVC you're working closer to the metal of the HTTP request/response cycle. WebForms abstracts away a whole lot of that for you.
Best of luck in your endeavour!
John is right.
However, have you heard of the "Empty Client" approach? This is a fairly new approach to developing .NET WinForms applications that can also run as web applications on plain browsers. That approach would allow you to develop your WInForms application and put it on the web if and when you desire with no additional development or adjustments.
One framework that does it is Visual WebGui