I am exploring WCSF and wondering how is the data access layer created? Some of the articles I have found are two years old and talk about using Web Service Factory. I am using VS 2010 and .Net 4.0. I am looking for some sample and tutorials with real world examples.
The Web Client Software Factory doesn't provide automated guidance for creating the data access layer. It's focus is primarily on providing guidance to facilitate composite Web application development (i.e. Web applications which are comprised of individual modules, often developed by different development teams).
There are several approaches for accomplishing data access, but a few resources you might want to check out are the ASP.Net MVC Nerd Dinner tutorial, the S#arp Architecture project, the Code Camp Server source, and the Microsoft Pattern & Practices Data Access Guidance. All of these use variations of the Repository pattern which is the predominate approach among teams following Domain-Driven Design.
There is a good reference implementation hidden in the WCSF2010 Source file, and a few other examples. On http://webclientguidance.codeplex.com, click Web Client Software Factory 2010 Source and then download WCSF2010Source.zip. Inside you'll find Trunk\Source\GlobalBankRI\GlobalBank.Commercial.EBanking (VSTS Tests).sln, which is a pretty good example of many aspects of WCSF, including data access through a WCF service. There are some other simpler examples in the Trunk\Source folder.
Only the ETF module is fully built out. Each view presenter uses an ETFController to manage data common to all presenters. The ETFController uses an instance of IAccountServiceAgent, realized by AccountServiceAgent (for non-unit testing), which is registered as a module. AccountServiceAgent uses a class that acts as a proxy for the WCF reference. The proxy instance to use, AccountServiceProxy, is hardcoded.
The actual source code for WCSF is in BlocksTrunk\Source.
Yeah, not at all easy to find. I don't remember what made me download this and look inside for such examples. Certainly not anything I read on the website.
I've used this example to build a web app that access SQL data and scrapes a website, if you'd like to take a look. It's still under development, but the data access bits are pretty firm: http://lcbodrinkfinder.codeplex.com/
Related
I recently stumbled upon ABP (previously Asp.Net BoilerPlate) as a framework to rebuild a web-app in a modular way. It's very interesting indeed, and come with a very wild bunch of basic elements like authentication, logging, security, multi-tenancy, settings and so on...
But, as far as I have understood it by now, ABP is "strongly coupled" with EF Core or Dapper, and I don't like to use ORM in my code, I have a more "database driven" approach and like to write queries myself.
So, the main question is: it's possible to use ABP WITHOUT using EFCore/Dapper? Or it's better to switch to other modular framework like OrchardCore or ExtCore?
EDIT: 11/11/2020 after #hikalkan reply.
Hi #hikalkan, thanks for your kind reply. Maybe I have to explain more what I want to achieve, so you can advise me better. My goal is to create a "pluggable" web-app, in which I can replace a module with another with same functionality but different details.
A little introduction: I have a "complex" web-app for HR departments of small-to-medium companies, many customers use it, and each one have its own copy installed in its premises. The app is composed by many functionality: personal data, contracts data, trainings data, shifts and so on. But each customer have slightly different modules, while the app itself is an old, monolithic one: it works, but I have to maintain different versions, almost one for each customer, very difficult and time consuming. Don't blame it on me, I have "inherited" the app and have to maintain and improve it that way.
But, finally, I can spend some time rebuild it from scratch, and I want it to be "modular", so that the main part (authentication, profiling, db interaction, theming, security, logging, etc...) stay stable & solid, shared among all installations, and each customer have a selection of module/plug-in to choose from. A bit like Wordpress, but better.
For example, let's say I have a simple module "contactSimple" for managing contacts (emails, phone numbers, pagers, and so on), each contact have a type and a value field in the database, very basic, and 90% of my customers are happy with it. But the remaining 10% want to add a note field, a flag "is main contact" or other minor changes. Now, what i want to do is: develop the "contactEnhanced" module as a separetad class library, with same interface and main functions of "contactSimple", compile it as a dll, simply change the dll in the web-app, update the database if needed to, reload the app and the new dll takes place, without altering any other component.
I was thinking to simply use dynamic reflection to obtain it, but then i found that reflection is not very suited, 'cause is slow and heavy on resources, so while surfing the web I find ABP.
Now, THE question: in your opinion, is ABP the framework/solution I was searching for? Please let me know!
ABP is designed to be database provider independent. It currently has two DB provider integration options: EF Core & MongoDB. That means ABP is not strongly coupled with the EF Core or Dapper: It works with MongoDB too. You set -d mongodb if you've created your solution with the ABP CLI.
So, the Framework itself has no relation to any database provider. But the pre-built modules have. For example, ABP provides an Identity module that has user and role management functions and needs to a database and includes some code to interact with the database. So it can't be db provider independent. All the pre-built modules provides EF Core & MongoDB integration packages.
If you want to use these modules (when you create a new application from the startup templates, some modules come pre-installed), you have to decide to use EF Core or MongoDB for the database operations of these modules.
When it comes to you own application code: You are free to use any approach, including ADO.NET with manual SQL queries. Just do it how you do in a regular application. If you want to isolate database queries, create your own repository classes. In this way, you don't see ORM in your code. But the modules still use EF Core or MongoDB.
Actually there a possibility to completely drop the EF Core references: Implement all the repositories needed by the pre-built modules yourself. Then they will work since they only depend on repository interfaces.
BTW; If you use OrchardCore, it uses YesSQL (Yes, YES SQL) as a core dependency and you can not change it because all the OrchardCore framework depends on it everywhere. Also, OrchardCore is UI dependent: It uses aspnet core MVC / Razor Pages UI while the ABP Framework is UI independent and provides 3 built-in options: Angular, MVC and Blazor.
Edit: After edit of the question
The story you've explained is one of the goals of the ABP Framework. ABP is highly modular and also extensible. We built all the modules to be extensible. For example, the module entity extension system allows you to add new properties to existing entities of a module (the module is used as a NuGet package) without touching its source code. You can override the server side logic of the module.
But modularity is hard in general. I mean the module also should be designed so extensible/replaceable. If you want to declare some interfaces for a module, so the module can be completely replaceable, you have a lot of restrictions. For example, you can not write SQL join queries to tables of that module (because the replacement module can use a different table structure).
However, if the customizations will be lighter, you can follow the ABP Framework's module design to make your module extensible/customizable. See https://docs.abp.io/en/abp/latest/Customizing-Application-Modules-Guide and https://docs.abp.io/en/commercial/latest/guides/customizing-modules (commercial docs will be moved to the open source side since they are available as open source now). BTW, ABP supports to load modules as dlls from a folder. It reads dlls and initializes modules on application initialization.
I can only explains what ABP offers. I can't make suggestion, unfortunately. Because a real life project is complex and I can't predict all the problems & requirements you will have in the future :)
The OP in this question asks about using an WCF/OData as an internal data access layer.
Arguments of using WCF/OData as access layer instead of EF/L2S/nHibernate directly
The resounding reply seems to be don't do it. I'm in similar position to the OP, but have a concern not raised in the original question. I'm trying to develop (natively) for a lot of different platforms but want to keep as much of the data and business logic server side as possible. So I'll have iOS/Android/Web (MVC)/Desktop applications. Currently, I have a single WinForms applications with an ORM data access layer (LLBLGen Pro).
I'm envisioning moving most of my business / data access logic (possibly still with LLBLGen or other ORM) behind a WCF / OData interface. Then making all my different clients on the different platforms very thin (basically UI and WCF calls).
Is this also overengineered? Am I missing a simpler solution?
I cannot see any problem in your architecture or consider it overengeenered as a OData is a standard protocol and your concept conforms the DRY principle as well.
I change the question: Why would you implement the same business logic in each client to introduce more possible bugs and loose the possibility to fix the errors at one single and centralized place. Your idea makes you able to implement the security layer only once.
OData is a cross-platform standard and you can find a OData libraries for each development platform (MSDN, OData.org, JayData for JavaScript). Furthermore, you can use OData FunctionImports/Service methods and entity-level methods, which will simplify your queries.
If you are running multiplatform development, then you may find more practical to choose platform-agnostic communication protocol, such as HTTP, rather than bringing multiple drivers and ORMs to access your data Sources directly. In addition since OData is a REST protocol, you don't need much on the Client side: anything that can format OData HTTP requests and parse HTTP responses. There are however a few aspects to be aware of:
OData server is not a replacement for an SQL database. It supports batches but they are not the same as DB transactions (although in many cases can be used to model transactional operations). It supports parent-child relations but it does not support JOINs in classic SQL sense. So you have to plan what you expose as OData entity. It's too easy to build an OData server using WCF Data Services wrapping EF model. Too easy because People often expose low Level database content instead of building high level domain types.
As for today an OData multiplatorm clients are still under development, but they are coming. If I may suggest something I am personally working on, have a look at Simple.Data OData adapter (https://github.com/simplefx/Simple.OData, look at its Wiki pages for examples) - it has a NuGet package. While this a Client Library that only supports .NET 4.0, part of it is being extracted to be published as a portable class Library Simple.OData.Client to support .NET 4.x, Windows Store, Silverlight 5, Windows Phone 8, Android and iOS. In fact, if you check winrt branch of the Git repository, you will find a multiplatform PCL already, it's just not published on NuGet yet.
I don't have a specific question here but I'm more looking for some guidance regarding a new software project I'm starting at work.
Here is a description of the project:
I am refactoring windows software that was written in Visual Basic 6 and uses MS SQL Server for a database. The code is tightly coupled with SQL queries and references old active X controls.
The software can run in a standalone mode where its only running one instance on one computer or in a distributed mode where it runs on several machines simultaneously all connected to a shared data source.
The users of the software need use of a wide range of USB devices that are integrated with the software on the client side. (I'm assuming this means the new version of the software needs to be a desktop application and can not be a browser based web application.)
The new version of the software is going to be updated to use new technologies in an effort to modernize the code and improve performance.
I would like the architecture of the new software be both logical 3-tiers and to use design patterns if appropriate. Although I am new to design patterns it seem like there is an opportunity to use the abstract factory, observer, and singleton patterns together in the new version of the software.
In a very generic explanation the software has an "employee" database table that stores information about employees. The client side has a grid view that allows the user to view the employee information stored in the database and to make modifications to the data through the grid view. Data can be added to the employee database by the client using forms that have text fields and drop down menus. Employee related data can also be captured by USB devices on the client side and then that data can be added to the employee database as well.
In terms of how this relates to architecture I'm guessing there could be an observable singleton employee object that is observed by data display objects like a grid view object and that these data display objects are created by an abstract factory method. (Does that make sense?)
The new software will be written in Visual Basic using Visual Studio 2010. Aside from that none of the other technologies have been decided upon.
I think we will use windows forms opposed to the windows presentation foundation although I'm not sure as there might be some image handling functionality that we want that is better done with WPF.
From what I've read I like the Entity Framework and Linq but I'm not sure how that works in conjunction with the business logic layer with the design patterns I mentioned above.
Also, I'm trying to understand if we could use the windows communication foundation and web services. This makes sense when the software is running in distributed mode but not much sense in the standalone single machine deployment. Adding web services and using IIS might be overkill for what we are trying to accomplish. I don't know.
So this is what I'm working on and what I've been reading about and researching. I would greatly appreciate your thoughts on this and any guidance you can provide.
Thanks!
Aside from the fact that you will learn a lot during the development process I can give you the following recommendations:
Use Stored Procedures in the database for database access. This will prevent concurrency problems and also allows for transactions. This means if something goes wrong (users computer crashes etc) then no data nor data integrity is lost
Treat the windows forms as simply 'interfaces' between the user and the database. Hence they shouldn't contain anything that keeps track of data (let the database do that) and they're only a means of gathering and showing data
I had a very similar experience.
I tried importing a VB6 database project that ran as a standalone app into VB 2005, and the code was very ugly.
One book that I found very helpful with doing three-tier DB applications using VB.NET (VB 2005, actually) was ADO.NET 2.0 with VB 2005 published by Murach. Got me up to speed very quickly, and it gave direct examples of writing three-tier DB applications (business layer, presentation layer, and DB access layer).
Can't remember for sure if there's a newer version of the book, but I was impressed with the layout of that one. It also deals with web apps.
Beyond that, I did some code generation to streamline hacking out the Object classes and the DB access classes for my project.
I believe this project is really going to have you learn and gain a lot of experience.
Like eddy556 said, use the forms only as interfaces. It works better that way.
Plus, if you have any problems, don't hesitate to ask. That's what we the StackOveflow team are here for anyway.
Good Luck.
Using VB.NET 2008
I want to know what is 3 Tier Architecture for windows application?
Can any one give a example of How to make a code for Inserting, Deleting, Updating in a database using 3 tier architecture.
Note am not asking a real code. Just give me a example.
From Multitier architecture
Three-tier'[2] is a client-server
architecture in which the user
interface, functional process logic
("business rules"), computer data
storage and data access are developed
and maintained as independent modules,
most often on separate platforms.
These days, a normal 3 tier application consists of a user interface written in Javascript, CSS and HTML which runs in the browser, a business rules layer which runs in a web server, and could indeed be built in VB.NET, and a storage layer which runs on a database server written in SQL and stored procedures.
Now it would be possible to do a user interface layer in VB.NET as a Windows application which then calls the business rules layer on the web server using a web services interface. This would give you more flexibility than the browser, and would not require learning as many APIs, however it is not common. It can really only be done in an enterprise situation.
This article has a simple VB.NET application that is a Windows GUI app, which call Google's web services API to do searches and to check spelling. That is a good example of a user interface layer. Then check this article for and exmple of a web service developed in VB.NET. This corresponds to the business rules layer, and in a real 3-tier application, it would be based around a database such as SQL server. If you were to use Access then it would not be a real 3-tier application. The database needs to be run on its own server and accessed across the network in order to be considered a tier.
The advantage of a 3-tier application is that you can scale each layer separately, and because each layer is simpler, scaling is also simpler. The DBAs can scale up to a database cluster, the business rules layer can scale up with a load-balancer and multiple servers, and the user-interface just gets replicated across as many clients as you need.
I don't know if is it the right way to use it, but I often use 3-tier int the following way:
One big Solution, with the name of the project
One dll project wich has the conection with the DB, using LINQ or whathever. Validating only the required fields of the DB
Another DLL project, wich has a reference to the project that conects to DB, and validate all data using the bussiness rules. Sometimes you may want a repositorium class wich has methods that can be used from the GUI layer
Finally, the GUI layer that can be HTML or WINForms, wich references to the bussines layer and calls all the appropiates methods, passing the data transparently and waiting for validation on the bussines rules.
You can comunicate with each layer using bool methods that returns true if everything is good, and personalized exceptions for each of the possible errors, and catch them on the upper layer.
I'll give you the gist of it. Real crash course.
You have three tiers:
DAL - Data Access Layer
BRL - Business Rule Layer
Presentation - The Forms, and such.
In the DAL, you configure how your application connects to databases, how it recieves datasets, etc. etc. Everything that has to do with data access.
In the BRL, you lay down how your program is going to handle the data it recieves from the DAL. Methods, and other things go in here.
And in the Presentation area, you simply make things purty and instantiate things from the BRL. The presentation area never has to touch the DAL, and that's the beauty of the 3tier layout. You can work on different areas and not step on other peoples toes.
I find the best way to understand it is to look at an example. If you go here:
http://www.codeproject.com/KB/vb/N-Tier_Application_VB.aspx
You can download an example and read the walk through for creating a very basic 3 Tier App in VB.Net. It's a little old in that it's a Visual Studio 2003 project but it should be easy enough to follow the upgrade wizard and get it up and running to check it out.
I'd like to give a brief overview about this style of programming and maybe I'll explain it in more details next time.
First of all, the 3-Tire concept engages dividing your program or application you are designing into 3 layers, the first layer is for manipulating the database in the operation called CRUD which stands for {Create,Read,Update,Delete} data from your database, using any kind of Databases : for example Oracle,SQLserver,MySql etc. That means you can connect your application with any type of databases without specifying a connection String to Only one database and we'll get more details about this next time.
The Second layer is Business layer which includes user data verification and other similar operations in which you process your business rules and the core of program,
The Third and Last layer is the Presentation layer which relates to User input and UI User Interfaces {The different forms for Input}
Frankly you can divide your Solution {Program,Application,Website} to sub-Programs to avoid data loss,organize your work, and to divide the development of your application among a team members.
in my point of view this is a great thing should be learnt in development, and as I was told by the grapeVine, if you want to enrich your knowledge and experience then you should be acknowledged about this important subject.
I work for a large state government agency that is a tad behind the times. Our skill sets are outdated and budgetary freezes prevent any training or hiring of new employees/consultants (firing people is also impossible). Designing business objects, implementing design patterns, establishing code libraries and services, unit testing, source control, etc. are all things that you will not find being done here. We are as much of a 0 on the Joel Test as you can possibly get. The good news is that we can only go up from here!
We develop desktop CRUD applications (in C++, C#, or Java) that hit the Oracle database directly through an ODBC connection. We basically have GUI's littered with SQL statements and patchwork code. We have been told to move towards a service-oriented n-tier architecture to prevent direct access to the database and remove the Oracle Client need on user machines.
Is WCF the path we should be headed down? We've done a few of the n-tier application walkthroughs (like this one) and they seem easy to implement, but we just don't know enough to understand if we are even considering the right technologies. Utilizing the .NET generated typed DataSets seems like a nice stopgap to save us month/years of work (as opposed to creating new business objects from the ground up for numerous projects). Is this canned approach viable for a first step?
I recently started using WCF services for my Data Layer in some web applications and I must say, it's frustrating at the beginning (the first week or so), but it is totally worth it once the code is deployed.
You should first try it out with a small existing app, or maybe a proof of concept to make sure it will fit your needs.
From the description of the environment you are in, I'm sure you'll realize the benefit almost immediately.
The last company I worked for chose WCF for almost the exact reason you describe above. There is lots of good documentation and books for WCF, its relatively easy to get working, and WCF supports a lot of configuration options.
There can be some headaches when you start trying to bend WCF to work in a way not specifically designed out of the box. These are generally configuration issues. But sites like this or IDesign can help you through those.
First of all, I would definitely not (sorry for the emphasis) worry about the time you'll save using typed DataSet's versus creating your own business objects. That is usually not where you will spend most of your development time. I prefer using business objects myself.
In you're situation I would want to implement a proof-of-concept first. One that addresses all issues you may encounter. This proof-of-concept should implement an entire use case, starting on the client, retrieving data from the database and returning it to the client. You should feel confident about your implementation before continuing.
Then about choice of technology. WCF is definitely a good choice for communication between your client applications and the service layer. I suppose that both your clients as well as your service layer will become C# applications? That makes things a lot easier since interoperability between different platforms (Java/C# for example) is still not trivial although it should work in most cases.
Take a look at Entity Framework (as there are a couple Oracle providers available for it already) in conjunction with .NET 3.5 SP1 which enables built-in WCF serialization of your EF generated classes.
Here is a good blog to get started: http://blogs.msdn.com/dsimmons
CSLA might be a good fit for your N-Tier desktop apps. It supports WCF, has a large dev community, and is well documented. It is very object oriented.