[ASP.NET, Design] Business Logic Layer or Stored procedures?

[Bazenga]

Hello,

I'm trying to see which route is best. Having a Business Logic Layer or have all the logic as stored procedures in the database.

The application architecture looks like this: Data Access Layer (LINQ to SQL) -> Business Logic Layer (Needed?) -> UI Layer (Web).

Does it make sense to have the middle layer if everything is done via stored procedures? If not, what do you recommend for the BLL? Could you advice on both routes? Advantages and disadvantages? Kindly note that the application is married to the database (Sql Server 2005) so there is no need to take into concideration that the dbms will change in the future.

Thanks.

[+Majesticmerc MVC]

I generally stick to the 3-layer architecture for my (admittedly quite small) ASP.NET systems. The business logic layer (even with stored procedures) allows you to add exception handling and more advanced input validation to your system between the presentation layer and the linq-to-sql layer, and for that I would recommend keeping it.

[Bazenga]

Thanks for your input. What kind of class naming do you recommend for this layer? The DAC layer already has the entity objects (like Item, Subject).

  On 25/01/2010 at 08:21, Majesticmerc said:

I generally stick to the 3-layer architecture for my (admittedly quite small) ASP.NET systems. The business logic layer (even with stored procedures) allows you to add exception handling and more advanced input validation to your system between the presentation layer and the linq-to-sql layer, and for that I would recommend keeping it.

[XerXis]

I always use both

1) Presentation layer

2) Business layer (most of the time i still use ado.net though) that calls stored procedures

3) Stored procedures that contains most of the transactional stuff

4) Database with foreign keys for data integrity

[garethevans1986]

One thing I cannot understand is why some developers have a layer which talks to the db using one entity type and then converts to another so the main application can then use it......all your doing is adding more for to your already long list of things to do! Designing a database properly will combat this. So you can in a sense merge one the entity layer and business logic layer into one.

Have a look at this: http://www.west-wind.com/WebLog/posts/160237.aspx

The code files are here: http://www.west-wind.com/files/conferences/conn_LinqToSqlBusiness.zip

Basically it's a DataContext lifetime management and factory wrapper class.

How to use it:

Create a new Project, create two folders with the project called "BusinessFramework" and "BusinessObjects". Grab the "wwDataContext.cs" and "wwBusinessObject.cs" files and put them into the "BusinessFramework" folder. I rename them to "<shortprojectname>BusinessObject.cs" and "<shortProjectName>BusinessDataContext" but rename them as you see fit.

Create a DBML file (called YourData, which then becomes YourDataDataContext) in the "BusinessFramework" folder, right click WITHIN the DBML, select Properties. Under "Base Class" set to "<shortProjectName>BusinessDataContext", Under Connection set "Application Settings" to False, "Connection String" to None.

Right click on the DBML select "View Code".

You *may* need to change the namespace on this class first, it'll depend. it should be the full namespace of where the file is..... eg:

someNamespace.projectName.Data.BusinessFramework

rather than

someNamespace.projectName.Data

it should look something like this:

    public partial class DBMLNameDataContext         
    {

        public DBMLNameDataContext()
            : base(ConfigurationManager.ConnectionStrings["YourConnectionStringNameFromApp.Config"].ConnectionString, new AttributeMappingSource())
        {
            OnCreated();
        }

    }

Create an app.config file within the root of the Project. Add a new Connection String, putting the correct name into the class above.

Add a table into the DBML.....this will be signified by <entityName>

Create a new class file (within "BusinessObjects" folder) called "Bus<entityName>.cs", we have here tbl_Engineer which is named "Engineer" in the DBML, so the file becomes "BusEngineer.cs".

public class BusEngineers : <shortprojectname>BusinessObject<tbl_engineer, YourDataDataContext>
    {
    }

Within the root of the Project create a new class file called "<shortProjectName>DataFactory.cs", within this add:

        public static BusEngineers GetEngineers
        {
            get
            {
                return new BusEngineers();
           }
        }

So to use the whole Data Layer....in another project add:

<shortProjectName>DataFactory.GetEngineers. => this will then list all your public methods within your BusEngineer class.

You could even move all the Business Objects out into another project if you needed to.

Done - I think.....any questions feel free to PM me.

GE

[Bazenga]

Thanks a lot, I'll look into that :).

  On 25/01/2010 at 11:04, garethevans1986 said:

One thing I cannot understand is why some developers have a layer which talks to the db using one entity type and then converts to another so the main application can then use it......all your doing is adding more for to your already long list of things to do! Designing a database properly will combat this. So you can in a sense merge one the entity layer and business logic layer into one.

Have a look at this: http://www.west-wind...sts/160237.aspx

The code files are here: http://www.west-wind...SqlBusiness.zip

Basically it's a DataContext lifetime management and factory wrapper class.

How to use it:

Create a new Project, create two folders with the project called "BusinessFramework" and "BusinessObjects". Grab the "wwDataContext.cs" and "wwBusinessObject.cs" files and put them into the "BusinessFramework" folder. I rename them to "<shortprojectname>BusinessObject.cs" and "<shortProjectName>BusinessDataContext" but rename them as you see fit.

Create a DBML file (called YourData, which then becomes YourDataDataContext) in the "BusinessFramework" folder, right click WITHIN the DBML, select Properties. Under "Base Class" set to "<shortProjectName>BusinessDataContext", Under Connection set "Application Settings" to False, "Connection String" to None.

Right click on the DBML select "View Code".

You *may* need to change the namespace on this class first, it'll depend. it should be the full namespace of where the file is..... eg:

someNamespace.projectName.Data.BusinessFramework

rather than

someNamespace.projectName.Data

it should look something like this:

 public partial class DBMLNameDataContext 
 {

 public DBMLNameDataContext()
 : base(ConfigurationManager.ConnectionStrings["YourConnectionStringNameFromApp.Config"].ConnectionString, new AttributeMappingSource())
 {
 OnCreated();
 }

 }

Create an app.config file within the root of the Project. Add a new Connection String, putting the correct name into the class above.

Add a table into the DBML.....this will be signified by <entityName>

Create a new class file (within "BusinessObjects" folder) called "Bus<entityName>.cs", we have here tbl_Engineer which is named "Engineer" in the DBML, so the file becomes "BusEngineer.cs".

public class BusEngineers : <shortprojectname>BusinessObject<tbl_engineer, YourDataDataContext>
 {
 }

Within the root of the Project create a new class file called "<shortProjectName>DataFactory.cs", within this add:

 public static BusEngineers GetEngineers
 {
 get
 {
 return new BusEngineers();
 }
 }

So to use the whole Data Layer....in another project add:

<shortProjectName>DataFactory.GetEngineers. => this will then list all your public methods within your BusEngineer class.

You could even move all the Business Objects out into another project if you needed to.

Done - I think.....any questions feel free to PM me.

GE

[+Majesticmerc MVC]

Yeah I should probably mention too that I work mostly in ADO.NET, where business logic layers are pretty standard, so the method that Gareth mentioned might be more suited for you, although only you can make that decision :)

[garethevans1986]

Any problems gents feel free to drop me a PM.

GE

[garethevans1986]

A correction to the above post....because of this:

https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=361577&wa=wsignin1.0

namespace CompanyName.ProjectName.Data.BusinessFramework
{

    // DO NOT REMOVE
    using System.Configuration;
    using System.Data.Linq.Mapping;
    // SEE HERE - https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=361577&wa=wsignin1.0
    // GE, 26/01/10

    public partial class DBMLNameDataContext
    {


        public DBMLNameDataContext()
            : base(ConfigurationManager.ConnectionStrings["YourConnectionStringNameFromApp.Config"].ConnectionString, new AttributeMappingSource())
        {
            OnCreated();
        }

    }
}

[sbauer]

I rarely use stored procedures anymore. I used to use them religiously. I had one for every function in the system. Looking back now I wonder what I was thinking. What a waste that was.

In most of my applications, I typically use an architecture that many people call the Onion Architecture. I design my apps so that they're testable (automated testing, not F5 testing) because it's important to me.

I'll have a bunch a repository classes that interface with my database via nhibernate, domain classes and service layer classes, when they're required. Outside of those, I'll have presentation model classes for strongly-typed views.

[+Majesticmerc MVC]

  On 26/01/2010 at 15:59, sbauer said:

I rarely use stored procedures anymore. I used to use them religiously. I had one for every function in the system. Looking back now I wonder what I was thinking. What a waste that was.

In most of my applications, I typically use an architecture that many people call the Onion Architecture. I design my apps so that they're testable (automated testing, not F5 testing) because it's important to me.

I'll have a bunch a repository classes that interface with my database via nhibernate, domain classes and service layer classes, when they're required. Outside of those, I'll have presentation model classes for strongly-typed views.

Looks like a nice article, gonna give that a read. Cheers!

I must admit that I used to use Stored Procedures for ALL my SQL, and to be honest, it did little to nothing to help the structure of my systems. Now (since I'm fortunate enough to develop in ASP.NET (no MVC yet though which is a bummer)) I tend to take advantage of the ADO.NET dataset designer to handle all my SQL statements, which makes life much easier since I can manage the entire system from inside Visual Studio.

[Bazenga]

  Quote

I rarely use stored procedures anymore. I used to use them religiously. I had one for every function in the system. Looking back now I wonder what I was thinking. What a waste that was.

Could you tell us why it was a waste? I'm interested in knowing.

[garethevans1986]

Because your "business logic" should not be in the database...

[sbauer]

  On 26/01/2010 at 23:58, Majesticmerc said:

Looks like a nice article, gonna give that a read. Cheers!

I must admit that I used to use Stored Procedures for ALL my SQL, and to be honest, it did little to nothing to help the structure of my systems. Now (since I'm fortunate enough to develop in ASP.NET (no MVC yet though which is a bummer)) I tend to take advantage of the ADO.NET dataset designer to handle all my SQL statements, which makes life much easier since I can manage the entire system from inside Visual Studio.

Stored procedures are such a fun topic because many people love them. I did too. I loved how my code looked. I loved how I had SQL sitting in the database, not in my code. Eventually, though, I got tired of it like you. I don't use ADO.NET dataset designer because I don't feel it scales well to larger systems and starts to break down.

It's unfortunate that you can't use MVC. If I never work in a WebForms project again, I'll be happy.

  On 27/01/2010 at 07:35, Ali Koubeissi said:

Could you tell us why it was a waste? I'm interested in knowing.

  On 27/01/2010 at 10:02, garethevans1986 said:

Because your "business logic" should not be in the database...

That's part of the reasoning behind it.

We use unit tests on our projects. Our unit tests ensure that 1) our features work as designed and 2) our features still work even after we've added new features. When you add business logic to stored procedures, you're beyond unit tests now. Unit tests need to be fast, and isolated - a small unit. Testing the database is not quick, and it's not a small unit. You'll need to create integration tests and those will be much slower. When things run slow, people tend not to use them.

Another reason is that I stopped generating most of my SQL by hand. No more CRUD sprocs, or adhoc statements. NHibernate takes care of that for us. If we have a very complicated query that we need to execute and the query looks pretty ugly while using the NHibernate API, then we'll generate the SQL by hand.

So far, so good. We'll have a repository that inherits from a base repository for each entity in the system.

    public abstract class RepositoryWithTypedKey<KEY,ENTITY>: IRepositoryWithTypedKey<KEY,ENTITY> where ENTITY: class 
    {
        protected ISession session;

        protected RepositoryWithTypedKey(ISession session)
        {
            this.session = session;
        }
        public ENTITY Get(KEY id)
        {
            return Session.Get<ENTITY>(id);
        }

        public ENTITY Load(KEY id)
        {
            return Session.Load<ENTITY>(id);
        }

        public IEnumerable&lt;ENTITY&gt; GetAll()
        {
            return Session.CreateCriteria&lt;ENTITY&gt;().List&lt;ENTITY&gt;();
        }

        public void Save(ENTITY entity)
        {
            Session.Save(entity);
        }

        public void Update(ENTITY entity)
        {
            Session.Update(entity);
        }

        public void SaveOrUpdate(ENTITY entity)
        {
            Session.SaveOrUpdate(entity);
        }

        public ISession Session { get { return session; } }
    }

    public class EmployeeRepository: Repository<Employee>, IEmployeeRepository
    {
        public EmployeeRepository(ISession session) : base(session)
        {
        }

        public IList<Employee> SearchByLastName(string lastName)
        {
            var criteria = Session.CreateCriteria<Employee>();
            criteria.Add(Expression.Like("LastName" + lastName + "%"));
            criteria.AddOrder(Order.Asc("LastName            return criteria.List<Employee>;();
        }

    }

And the controller

public class HomeController : Controller
    {
        private readonly IEmployeeRepository _employeeRepository;

        public HomeController(IEmployeeRepository _employeeRepository)
        {
            this._employeeRepository = _employeeRepository;
        }

        [HttpGet]
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        [ActionName("Index")]
        public ActionResult IndexSearch(string search)
        {
            return RedirectToAction("Search", new { searchTerm = search });
        }

        [Transaction]
        public ActionResult Search(string searchTerm)
        {
            if(string.IsNullOrEmpty(searchTerm))
                return RedirectToAction("index");

            var model = new HomeControllerViewModel();
            model.Employees = _employeeRepository.GetEmployeeListByLastName(searchTerm);
            model.Search = searchTerm;
            return View(model);

        }

    }

[garethevans1986]

I've come accross NHibernate, Fluent NHibernate and Dependency Injection before.

The only problem I have with NHibernate is how do you script the changes to keep your SQL Servers up to date?

GE