I am supporting an ASP.NET app, which is installed on a web server and a VB6 app installed on a different app server. There is code duplication in the VB6 app and the ASP.NET app. I want to use some of the code in the ASP.NET app in VB6. I believe I have three options:
Expose the required functionality in an ASP.NET web service. The VB6 app will consume the web service.
Rewrite a small section of the vb6 app in .NET and extend the asp.net app. This will eliminate some of the code duplication.
Setup a class library for the ASP.NET app. Install the vb6 app on the web server. Expose the required functionality from the class library in a type library.
Which option is best? I believe option 2 is best.
Option 1. That leaves your shared, already-tested code on the most modern platform.
This is very hard to answer, as it varies for each company and each situation.
As a general rule, I'm very much in favor of using web services where possible, especially if multiple applications are using the same logic for the following reasons:
If I have to change the logic, I can do it in one place and fix all apps that depend on it
The same can be said for database connection strings, etc.
A bug fix can also often be fixed in one place.
I've had difficulties with a particular database that I need to deal with, where the vendor's updates tend to break their .NET adapter. Twice I had to modify/recompile a ton of apps to resolve this. Since then, we made it a policy to connect to that DB only via web services, so I'll only need to update one app in the future.
When developing mobile apps, the simple fact that we already had all our code in web services makes it that much easier to write apps that are strictly UI and leaving the business/database access logic as-is in existing web services.
All of those are pretty much "Standard" arguments for the SOA approach.
All things considered, my first recommendation, not knowing your specifics would be option #1.
There is a fourth option - a total rewrite of the VB6 app, if it's feasible, and if you can convince those who control the budgets and time allotment. Even with that, you can use the Service Oriented Architecture and split much of the logic into web services.
Related
I'm brand new to C#/.NET
Why does ASP.NET have so many different choices of projcets? (Web Application, Web API, Web Site, MVC ect). I just want to listen on a tcp port, and a way to send a response. If there are libraries to help me do routine stuff like constructing the HTTP request, parsing the header, ect - then cool. But I don't want a super opinionated framework that tries to do everything under the sun.
Why do I need IIS at all?
Addressing your points in reverse order, first - why do I need IIS?
The answer is, maybe you don't. If you are doing a simple listener that won't be exposed to the public internet, then you don't need it.
If you are doing a web application that needs to scale, be robust and easy to manage then it can help you with:
Logging
Operating in a multi-server environment for scale/high availability
Handling multiple requests in an isolated way
Serving multiple applications from the same host with sandboxing to ensure each application has guaranteed resources (memory, CPU)
Application lifecycle management
IP address restrictions
support for FTP, CGI, WebDAV
URL rewriting
Response header manipulation
Failed request tracing
Protection against some DoS exploits like slow HTTP attacks
Etc.
In short, it is an industrial strength, real world web server that will keep your application up reliably in a hostile world and scale as your application grows. it is certainly overkill for some cases if you don't need this kind of scale/high availability/management capability. In those cases you have the option to self host ASP.Net in a Windows Service or even a console app. This might sound complicated, but it has been made pretty simple by OWIN - Open Web Interface for .Net. This is an abstraction of the interface used by Asp.Net to communicate with its hosting server.
There is a very good tutorial on how to self host web API in a console app here
http://www.asp.net/web-api/overview/hosting-aspnet-web-api/use-owin-to-self-host-web-api
It does exactly what you ask for in your comment:
You create a console app project
You add references to the right assemblies (the tutorial uses NuGet to download the assembly packages)
You code up your web operation logic
You compile
You run the resulting exe
That's it!
On your second point about ASP.Net - it is a framework that has gone through a lot of evolution trying to keep up with very rapid changes in the web development world. This meant it got a bit bloated and lost some of its coherence, but recently the developers have been focussed on making it more lightweight, more modular and simpler. Scott Guthrie summarises it in his blog:
http://weblogs.asp.net/scottgu/introducing-asp-net-5
Why does ASP.NET have so many different choices of projcets? (Web Application, Web API, Web Site, MVC ect). I just want to listen on a tcp port, and a way to send a response. etc...
Because each project has its own purpose.
If you want to just listen on a TCP port then you could go learn Microsoft's Katana OWIN (but I highly doubt if this is what you want).
Katana OWIN
Briefly going through each projects purpose:
"Web Application" actually opens up another window and lets you choose from the following:
Web API is for exposing RESTful services or JSON data.
Web Forms is for making web pages that use Web Form components.
(A bit like Windows Forms, but Web)
MVC is for making Model-View-Controller web applications. This is where you build components with a separation of concerns. Model for data. View for what the user sees. Controller for controlling how your page behaves.
Why do I need IIS at all?
IIS is for serving .NET applications.
Without it, it would be quite hard to serve .NET applications.
I'll start with 2 then move on to your first question. IIS will run whatever the .NET web service you need, be it a monstrous WCF service, an ASP.NET application or the most basic http handler.
To my knowledge, ISS is the most straightforward way to use .NET web services. If you are used to PHP, it's basically LAMP or WAMP for .NET, which means it is sort of necessary. There are alternatives, as Mike Goodwin points out, but I have to admit I am not familiar with those third parties. Since replacing a layer for another doesnt mean much, I would stick to the "normal" procedure.
Since you dont want the framework to do a truckload of operations for you, your best bet might be along those lines:
Create a basic ASP.NET projet
Remove the default ASP.Net page because it seems you dont want it
Add a Generic Handler to your project. This will result in a myFile.ashx, which handles http requests and let you build any response you want
Of course, if you dont want to bother with IIS configurations, you'll need someone to setup an URL on IIS and map it against your handler repository.
EDIT:
"Abstraction layers" would be the very definition of frameworks, for good or ill, so you're stucked with it.
Now, since you have a low level background a not-so-intrusive way to work with the .NET web services would probably be the three steps I suggested earlier. You are still stucked with IIS though, in order handles the communications (i.e. manages sockets/requests). That's the way the framework works.
STILL, THERE IS HOPE. If you have complete control over your server (which is not my case, some other IT team manages the web servers), you certainly could build a windows service that listens to some socket and work the requests accordingly. It is a most unusal solution if you want to serve web pages, but would work rather well if you only want to push some data through http requests. If you go down this path, I suggest you take a look at the System.Net namespaces, you'll find some classes like "Socket" there. Combined with a console application or a windows service, you could work something out.
One of my coworkers is former microcontroller designer, I know exactly what kind of feeling you have towards the .NET framework. You'll go through some frustrations at times, but most of the time there are work arrounds. Feel free to request more details if you need some.
Are there any good books or websites on this subject covering subjects like:
different migration scenario's (big bang, module for module, function for function) pros and cons
do's en dont's
tooling
handling customer expectations
We have a rather large winforms based product which we would like to migrate to the web. Migrating in a 'big bang' scenario would probably take at least two years. We're looking for alternative scenario's.
I'm especially looking for ways to handle the inbetween scenario, what options do you have to keep customers happy.
Let them use the windows application at the same time as the new web
application?
Let the windows application use the new features from the web
application via a service interface?
Accept the cost of double maitenance for a while to keep customers happy?
You are more likely be doing a complete rewrite. Because web is conceptually different from windows forms, there would be a lot of changes.
Your best bet is stop new development on windows forms app. Start writing a new app for the new features. Then start moving one isolated feature at a time to web.
You have two options for the UI
webforms - matches closely with windows forms model. If you are
using any 3rd party controls like devexpress, you can find the
equivalents in webforms.
mvc - It is more like re-architecting the whole presentation layer.
If your UI layer is already separated from business layer, then it
would be a good choice to go down the path of MVC. However the
development experience is totally different from doing windows
forms.
State
Maintaining application state is comparatively simple in windows
forms. In webforms you have viewstate to do that for you. But you are going to run in to rude shocks as you run into limitations of viewstate, especially when it gets too large.
In MVC, you are completely responsible for maintaining the state.
New skills
You require new skills to mimic state-full scenarios
Strong understanding of javascript, ajax, at least one javascript
framework like jquery. 3rd party commercial tool kits can ease some
of these pains.
Depending on complexity you might need web application frameworks
like Backbone.js /Knockout
Expectations
It would be very expensive to achieve the same responsiveness as windows app, as you will be messing with multiple technologies. Probably your users are going to hate the new app initially. Having skilled web designers on staff is very important
Based on our own experience with moving applications from desktop to web: carefuly inspect the architecture of your winforms applications and if possible - try to provide a web interface at the service or persistence level so that your windows applications use web services instead of directly talking to the database. Then you can let your users launch desktop modules from the application server using clickonce.
Such approach let us move to web quickly and users got the same GUI and a new way to access the application. In fact, it took like 3 or 4 months to redesign existing applications so that they use web services.
Then, we were replacing modules one by one, implementing them as web applications and maintaining both (clickonce and web) for a short period of time so that users were able to get used to new modules.
The migration of consecutive modules from clickonce to web was prioritized in an obvious way - we've started from modules that were used by most users. In fact, the initial release of the system has only one web forms module ready and remaining modules are being replaced for over 2 years now, one by one.
Can I convert a non-MVC asp.net application to be Azure compatible ? Or If i want to create an Azure web application, should it be MVC one ?
The other answers answered your question about converting your app to MVC for deployment to Azure (you don't need to).
If you're creating a new web application and go with ASP.NET MVC (which I'd recommend), just remember if you go with MVC3, you may have to make some of the MVC3 DLL's CopyLocal for your deployment, as it won't be part of your web role instance. At least that's how I still understand it. The 1.4 SDK of the Azure SDK doesn't have a MVC3 Web Role template yet.
See this post on steps to get your MVC3 app Azure-ready.
Hope this helps.
You may take a look at the following blog post for migrating an existing ASP.NET application to Azure. It should not necessarily be an ASP.NET MVC application. Any ASP.NET application will work.
azure has 2 roles
1. a webrole
2. worker role
web role is nothing but an asp.net app. so no need to convert it into an MVC app just any asp.net thing will do fine
Yes, you can. But you need to be aware of certain limitations too, none of which were mentioned in the answers already given:
Your application should be stateless, unless you are running a single instance (for most apps 99,9% reliability is OK, but there are some where you want 99,95%, so you need at least two instances + it gives you additional benefits of a load balancer, etc.). The reason for this is that if you have more than one instance, the load balancer will deliver the request to a different instance. You can use AppFabric Cache to solve this.
You don't have a file system - this is not entirely true, but in reality you should never rely on having local files. All you image uploads (e.g. user profile pictures) should be uploaded to a blob storage and linked to there. How you do this is another matter, and one that can be approached differently depending on the architecture of your existing application. You can get away with files, by using Azure Drive, but it's slow as hell.
No Event Log / RDP - this is also only partially true, but you should rely on other ways of getting diagnostics information from your role. While you can RDP to your role instance, there are better ways (e.g. Azure Diagnostics storage).
Database should be chosen carefully. Sure, you have SQL Azure available, but it's expensive (1 GB = 10 USD/ month). If you can get away with stuff like Table Storage, you may save on some costs. Again, this depends a lot on the architecture.
As for the second part of your answer. MVC as a pattern is nice. It saves you a lot of time, it's much more adapt for the Web as WebForms ever will be. The event based system was designed for Desktop applications, and it was forced onto the web. However, going to Azure does not imply a requirement to go to MVC. What I suggest you do however, is treat it as a nice jump-start opportunity to look into MVC and see how it could help you write your apps better & faster.
As with any other case involving architecture of apps, it depends. If you used common patterns (e.g. IOC, Repository), you will have a really easy time moving any app to Azure.
I am starting a new project which will need a ASP.NET MVC 2.0 website, a Silverlight section and a Windows Phone 7 UI.
My plan was to use WCF RIA Services to create a set of services which would be used in all different UI projects. With the Silverlight project I would use the standard tool integration, the Windows Phone looks like it may have to be WCF Services exposed by the RIA Domain Services, but I'm not sure about the ASP.NET MVC website.
My initial thoughts I would simple reference the class library containing the Domain Services and use them directly. Could this be considered a viable approach to using RIA Domain Services in a ASP.NET MVC website?
Kind Regards
Michael
I know a long time has passed since this question was asked, but since I had to make such a decision, I might as well document it for the benefit of others.
I work in an environment where lots of legacy and new apps co-exist, with the legacy apps being phased out. So we've had to build interoperability between everything from MS Access, to web service end points in C#, VB, Web Forms, MVC 3, even Flex, Reporting Services...the list goes on.
One of the biggest pain points in a multiple-client scenario is the maintenance of interoperability over time. As data, requirements and delivery mechanisms change, keeping things smooth ends up taking a lot of resources.
My approach has been to create one and only one mechanism for reading a given source of data by defining 1) a model, 2) a serialization/deserialization layer and 3) a service layer. All projects that need to use XY_Data must use the XY_Service to get XY_Objects via the XY_Serializer. Direct db calls or stored procs, etc are allowed in the XY_Application. This allows me to drop in replacement DLLs (versioned) with bug fixes and upgrades without restarting anything. I hardly ever do a full publish.
So yes, what you're suggesting will work. I would recommend only that you rigorously enforce the single-source-of-truth and DRY policies both in your data and your APIs.
Is there a business case for using WCF WITHIN your web application (ASP.NET/SQL Server)?
I'm not talking about a service to be consumed by others, but rather a service to be consumed WITHIN the web app. So far, the only use for web services WITHIN the web app I came up with is when I need to call the database from the client (through AJAX).
Please don't give me the copy/paste lesson on web services, all I'm looking for is a CONCRETE EXAMPLE of WCF benefiting the web application, and NOT the other apps consuming the services.
Quick clarification: by "web application" I mean a self-contained CRM of sorts. It does a lot, but it DOES NOT talk to any external apps/db's, and DOES NOT need to have service points open for other apps to consume.
We have a Windows service that gathers live data from the web. Because the data is ephemeral (it's only really valid for around 3 minutes), there's no point in recording it in a database. To retrieve data, the Windows service offers a (TCP transport) WCF interface which is only exposed to the web-server, from which our web-app requests data.
I think it very much depends on how you define "application".
If you're talking about a single web application then with the exception of provision ajax data as you've already noted I'm struggling to think of a generic reason why you'd want to as a web service (even more so for WCF) is just an exposed API and if you're in the application surely it would be better (in all kinds of senses) to go straight to the API without the additional overhead of wrapping and unwrapping the calls and the data - which is pretty much redundant.
On the other hand if by "application" you mean an assembly of "stuff" that delivers a solution to a set (or even various sets) of end users then yes, of course... there is definitely a case where the flexbility of having components communicate via services outweights the overhead issue. Where it gets grey is if there is an assumption that a single application will (or at least might) later become multiple applications wired together - but if you're not doing it now then you're just causing yourself pain you don't need so shouldn't bother. If you need to split it deal with that as a self contained exercise as and when you need to split it.
One concrete example from my practice: On one web site we use actively tables which are implemented with respect of jqGrid plugin to jQuery. The contain of grids will be loaded per ajax. So the most pages of the web site are very simple and have clear XHTML code. The business logic with the interface to the database is inside of WCF service. Inside of WCF service we get data also from other information stores of the organization. In the same way if one will need later to have an input from our project the WCF service will be perfect.
So the usage of WCF WITHIN in our web application helps to archive clear interface, clear separation business logic from the HTML markup and better testability (with utit tests integrated in Visual Studio).