it took me longer to write a DDD application than my previous approach using my Extremely interesting articles, thank you! of a method to add a new Review to a Book. In this article on sample shopping tutorial application, we will focus on domain and domain logic, without worrying about data persistence. Also, its a pure .NET object (POCO class) and persistence ignorance (PI).

code. ), and I dont like writing repetitious Adding connection string and injecting EShoppingTutorialDbContext via AddDbContext command in ConfigureServices method in Startup class. If you continue to use this site we will assume that you are happy with it. So, right click on solution Explorer, and choose Add --> New project. What is the reason to add review to a collection instead add review with a reference to a book as a value object? external references, so the entity classes didnt know anything about EF Core or no right answer. to do the job. From experience knew where to look and I came out with a library called EfCore.GenericServices. Maybe Someone else might use a very different approach to DDD, but hopefully and Aggregates). In the diagram below I have a trivial requirement to update the publication date of a book. Hi Jon, Next we add .NET Core Class Library in Framework.Core folder and naming it Shared Kernel, as shown in the image below: Shared Kernel Library is where we want to put our public models and helper classes, which will be used among all libraries in the entire solution. I dont have an example of type 3 business logic in my own code, but I was called in towards the end of the project to help out and it wasnt appropriate to add my EfCore.GenericBizRunner and the BizLogic and BizDbAccess layers so I just build classes in the ServiceLayer to hold the business logic. doing validation checks via code, for validations that cant be done by validation attributes. Fo me personally domain is a clean layer without infrastructure (data access). Found your blog while I was looking for reasons to get rid of repository pattern and mappers in an asp.net project!!! We start our application first by adding a Blank Solution, by opening Visual Studio 2019, selecting Create a new project on the right menu, selecting Blank Solution and naming it DomainDrivenTutorial, as shown in the image below. As you see in the image below, the application logic is dependent on Customer Repository Interface not on concrete implementation of repository, for more abstraction (Dependency Inversion Principle), this means that the application logic is completely ignorant of any implementation of customer repository and data access concerns, keeping the application logic codes intact and safe from data access changes in future, ensuring that it is less fragile and easy to extend. Create folders: Domain, Entities and Repositories, and add a new class naming OrderShould in Entities folder as shown in image below: OrderShould class will contain unit tests for order entity. Still my question is if we provide method name in the second parameter of UpdateAndSaveAsync(), will Generic Service still try to match the other methods? I just wanted to tell you that this library has been a life saver. I work for a hospital and have been building numerous CRUD apps for COVID19 to track supplies, beds, staffing, and much more to ultimately produce dashboards for the executive teams to make important decisions related to this crisis. However, After getting the success message for update-database command, go and check the database, a database called EShoppingTutorialDB with two tables must be created as we configured before in entity mapping configurations as shown in the image below: Alright, we have successfully created database and tables, so lets go and complete the other parts of the application like: unit of work, order repository and web API controllers. As you see in the code below, it is not an ordinary weak entity model that is used just for CRUD operations! Yes, with EfCore.GenericServices you can now have no database code in your clean layer. I really like DDD because I know exactly where and DDD approaches). Because its a library its worth minimise the amount of database access code in the entity class methods. IHope you dont mind, but I tweeted your comment see https://twitter.com/thereformedprog/status/1269203325452517376 Its nice to know it a) was used for such a good use, and b) that it speeded up your development! It shouldnt throw an exception so something funny is going on. Domain-Driven Design: supporting JSON Patch in Entity Framework Core, Architecture having to think about the database side at the same time. Glad you found the article and the EfCore.GenericServices library useful. After 20min reading your posts I was convinced to give a try to EfCore.GenericServices. Super-simple business rules, e.g. This code is longer, mainly because it handles the situation where reviews are already loaded and does some checks to make it more secure. It is a rich domain model, which combines data and logic together. So before going further, it is better to add the NuGet packages for entity framework core. of a SASS system using ASP.NET Core/EF Core. Its so great. But the extra bit was but all in one class. Having the ability to access the applications But I say again, one size does not fit all, if you have a simple application, or a micro service that in maximized state will only have eight or ten repositories, just keep it simple (kiss principle), and do the same, that we did. Three ways to securely add new users to an application using the AuthP library, Part6: Using sharding to build multi-tenant apps using ASP.NET Core and EF Core, Advanced techniques around ASP.NET Core Users and their claims, Building ASP.NET Core and EF Core hierarchical multi-tenant apps, Multi-tenant apps with different versions can increase your profits, Creating Domain-Driven Design entity classes with Entity Framework Core, Architecture As before, we explained in this article, we only add interfaces in application domain, not the concrete implementations. Lets really look at the extra code that DDD needs to work. Business logic that uses multiple entity classes, e.g. like what happens if the entity class isnt found, and what if the data in the The code is better but using a DDD approach can slow down According to this, Id place to Book and Review classes within Layer 1 (Domain). At first, we should configure the mappings of C# entity classes to database tables, like code below. the best library I have built so far. lots of situations. at GenericServices.Internal.MappingCode.EntityUpdateHandler`1.RunMethodViaLinq(TDto dto, String methodName, Object entity, CreateMapper mapper) EF Core came out that I felt I could build property DDD-styled classed (known You can also download source code, review the codes and test the result. Then we add a DbContext class file in Persistence folder naming it EShoppingTutorialDbContext, and so we apply those mappings in our DbContext class, as shown in the code below. Youre saying that you have dbcontext included when adding a review to a book because of the performance. Also, some of it repetitious (and boring! for handling the Reviews to the entity class method. Good question, isn't it? If thats what you are asking then the answer is yes. Notice that no repository implementation will be added to the application core domain. I would say I am back up to the Aggregate root i responsible for transaction. The fact that unit testing with a real database is easy with So, without connecting to any external service or database repository, we can easily write unit tests in order to check models behavior (business rules). approaches depending on the type and complex of the business logic. You can see a running version of this application at http://efcoreinaction.com/ and the code can be found in this GitHub repo. Very interesting article! add a Review to a Book (think Amazon reviews). So we can change anything we want in future in any other parts of application like: repositories, databases, ORMs, UI, etc. A six-month engagement on an already started ASP.NET public int BookId { get; set; } NOTE: Some people dont think its right to unit test with a real database, but I find it works for me. at System.Dynamic.UpdateDelegates.UpdateAndExecute5[T0,T1,T2,T3,T4,TRet](CallSite site, T0 arg0, T1 arg1, T2 arg2, T3 arg3, T4 arg4) Now let's go and build a simple ASP.NET Core Web API application in order to better understand the domain driven design implementation approach. nut, or in software principle, KISS (Keep it Simple, Stupid). To offset the extra code of DDD I have built two However, there is an issue with EfCore.GenericServices that Choose Microsoft.EntityFrameworkCore and on the right section, select EShoppingTutorial.Core project, and then click on Install button as shown in the image below. that is super-simple up to super complex. So, we added a Order DTO models, now we must configure it, in order to config order entity to map order items via constructor, like code below: Alright, we are almost done, now we can run and call the API services, with the postman or swagger. The most famous architecture for implementing DDD is Onion architecture, as shown in the image below: Application Core (domain models and domain services) where business logic lies in there, is not dependent on any data persistence tools or any technology, so we can say, that our application core domain is independent of the outside environment and external dependencies, so that lead us to (testable and agile architecture principles), because our application core business logic doesn't depend on other parts of the application like database, etc., so it can be easily tested and debugged in isolation, thats so great. DbContext means I have a get out of jail card if I need to do something and Thank you so much for sharing this. of Business Layer working with Entity Framework (Core and v6) revisited, https://github.com/JonPSmith/EfCore.GenericServices, Wrapping your business logic with anti-corruption layers, Creating We add mapping class files called OrderMapConfig and OrderItemMapConfig in Mappings folder, and then we put entities mapping configurations. EF6.x library called GenericServices. That means that the entity class has no external references, so the entity classes didnt know anything about EF Core or its DbContext. If you really have a simple data driven application, with minimum business logic, that you are sure it will rarely change in future, so don't do that, just keep it simple (kiss principle). of Business Layer working with Entity Framework (Core and v6) revisited, Right click on application solution name and click Manage NuGet Packages for Solution. As Martin Fowler in his book, Patterns of Enterprise Applications Architecture says: a Repository mediates between the domain and data mapping layers, acting like an in-memory domain object collection, that isolates business entities from the underlying data infrastructure. If youre adding a review without checking others belonging to a book, then maybe review should be your aggregate root instead? do I handle that? For this business type I tend to just create a class/method That means I separate the business logic from the database access code by Oops, sorry for the bad formatting obviously WordPress doesnt honor HTML formatting. features linked to one entity/area I would typically put a method for each function, Note I had to edit your works a bit to fit twitter. I find that business logic ranges from something edition covers EF Core 5. Alright, so far so good. We create a Models folder in it, then we add PageParam class to make data pagination request model, that will be used later between repository and application services layer. So lets write some unit-tests together for Order entitys business rules. I have now used DDD and my supporting libraries for two years on my own projects and client projects. If there are a several different business have the collection of Reviews loaded, so how do we handle this? at GenericServices.Internal.Decoders.MethodCtorMatch.ToString() Understanding and implementing Domain Driven Design Implementation Approach. With my experience of writing the original GenericServices library I After 3 hours coding and try to figure out how this lib works I m really amazed (and my project about a dozen Interfaces and classes less)!!! For example, I have overridden the Add method of the base repository in order to change its behavior adds a new order. Sorry I didnt reply before, but Disqus didnt alert me. That works OK, but you dont get the level of separation that type 4 gives you. I have a question. creating a specific repository class for just that business logic. That is MUCH faster, especially if you have hundreds of reviews. Here are the bigger client projects where I used an DDD approach: This article looks at what I have learnt along the way. Shouldnt it just call the method that we supplied? But the main point is that it doesnt need to load the existing reviews to add a new review it just adds a single review. This section gives a more nuanced Right click on solution name and create a new folder and name it EShoppingTutorial, then add a .NET Core class library project by going to File -> New -> Project, and name it EShoppingTutorial.Core, like the image below: Next, we want to define the application solution structure, to separate files in folders like: Domain, Entities, Services, Persistence, Repositories, etc., in order to separate application business logics of data persistence concerns for having a better and clean application architecture, like the image below: I want you to have a closer look at the application solution structure before coding, we have separated the folders, next we will add some classes to them, this can lead us to having better application architecture (Clean Architecture Principle), better refactoring and maintenance. Right click on application solution name and click Manage NuGet Packages for Solution. I want to use the code to extend my apis. and also in my book Entity Framework Core in Action chapter 4 I described the Alright, finally we're done! God bless you Jon Smith. Article seems well made and properly explained, at a first glance. I liked it very much. at System.Linq.Enumerable.SelectListIterator`2.MoveNext() It depends on so may things. The library is helpful because it can adapt the input and output of the business logic, which helps to handle the mismatch between the business logic level and the front end bit like a mini DDD anticorruption layer (see the article Wrapping your business logic with anti-corruption layers). It does take Obviously for you you cant do that I would suggest a service in your infrastructure or ServiceLayer instead. As Scott Millett in his book Professional ASP.NET Design Patterns says: Methods that dont really fit on a single entity or require access to the repository are contained within domain services. No matter an exception has been raised or not, this method always will dispose the DbContext, t need to follow the DDD rules or implementing repository layer again, it will be over engineering so we just keep it simple, and we inject the DbContext directly in the controller class. m agree with you, but in this imaginary sample tutorial, I just wanted to show the whole structure of domain driven implementation, and in real world scenarios the implementation method of MoneySymbols will not be suggested. That works, but some people dont like having the DbContext accessible It has properties and behaviors. The domain service layer can also contain domain logic of its own and is as much part of the domain model as entities and value objects. Not quite sure what you are asking. In this article, I'm going to guide you through creating an application using Domain Driven Design Implementation Approach, with Generic Repository Pattern and Unit of Work Pattern in ASP.NET Core 3.1 Web API and Entity Framework Core 5.0. So in software designing always, don't forget to separate things that can change from things that doesn't change. For more information about Unit of Work design pattern, you can just type few words in Google like: "martin fowler unit of work". I have found my EfCore.GenericBizRunner library A four-month project design and build an adapter description of what I do in real applications. As you see in the code below, Ive created a simple class that implements the IUnitOfWork and IAsyncDisposable, and at the time it only has one repository, if you in future need to add other repositories like: customer, or basket repository, just create and add them in this class. The DDD approach says that a NOTE: Im not explaining why I use a backing field, _reviews, in this example. I suggest you have a look at my article Creating Domain-Driven Design entity classes with Entity Framework Core for why I do that. between two security systems this had complex business logic.

its DbContext. All right, now its time to add a class called OrderRepositoryShould in EShoppingTutorial.UnitTests project -> Repositories folder, in order to test behaviors of order repository. No prob. approaches to Domain-Driven Design with Entity Framework Core, GenericServices Hi Jon, Your call looks OK (NOTE: because you called the DTO RemoveReviewDto it will look for a method called RemoveReview). So this class will hide and encapsulate the data of OrderItems and related business rules, and will perform its duty as an aggregate root entity. working on medium sized web apps I find there is a range of business rules. Object, with way too much going on inside it. business logic that it is a challenge to write, e.g. It very easy to mock the database, because the business library for handling business logic, but that that works the same for non-DDD It applies encapsulation and information hiding, as you see below, there is one-way relation to Order Items entity, and the only way to access the OrderItems data in application will be via this aggregate root rich entity model. using DDD. DTO is linked to. My design used a lot of DDD concepts Disque sometimes doesnt notify me of a comment. Nearly all of my libraries came about from a previous project where part of it didnt work as well as I thought it should and, on reflection, I came up with a better way to that part in future projects. Senior Microsoft.Net Developer, with more than 10 years of application design, development, and support experience. at System.Linq.Enumerable.SelectIListIterator`2.MoveNext() The work you put in to map DTOs to entities has really sped up my application dev time. action has changed, but its the same length. Design Philosophy + tips and techniques, Improving Then we add Framework.Core folder in Solution. Domain-Driven Design updates in EfCore.GenericServices, How means that the code is the only implementation of that function. Right-click the EShoppingTutorial.UnitTests project and select Manage NuGet Packages, and add NuGet Packages. Thats This is a comment with disqus moderation OFF, I am replying to the test comment with notification OFF, This is another test of disqus to send me an notification, I got a notification and I am replying to this test, This is a test to check Disqus is working propertly. Mainly because DDD functions are easy to find, test, and So before going further, we must add the NuGet packages for entity framework core, like image below. Im using DDD so I place business logic inside the entity classes as long as the business logic worked on the root or aggregate entities for instance, adding a Review to a book. To sum up, there are pros and cons allowing the DbContext being injected into the method call. because the entity class and its methods start to become an God And in case your neat libraries wouldnt exist, what would be your architecture? In order to access the complete source code, you can download it from Github. see EF Core docs where it defines After adding the repository, now its time to add a Unit of Work interface and implementation class. Last year I updated this library to be able to pre-load collections, which means it can add a Review to a Collection without the entity classes having to access the DbContext. Early in 2020 I realised I could change the EfCore.GenericServices library to load related navigational properties by providing an IncludeThen attribute which defined what navigational property(s) to load. That isnt what I, or my clients, want. to find, fix, and refactor. Did they extract all DB logic into a repository? I was just pointing out that GenericServices tries to match using parameters and the DTO name, thus saving you having to add the method name. This used EF Core and supported non-DDD in a similar way to the original GenericServices I combine the business logic and the EF Core database accesses But, over the last few years I have concluded that I should logic used a repository pattern to handle the database accesses. is an empty interface which tells EfCore.GenericServices which entity class the

adding all these extra features, which takes out other code you might have encapsulates the primary reasons I love DDD. Now you might say 9 lines isnt much, but in a real application you have That's enough talk, lets start the sample project. Sorry I missed your comment.

Youre saying that you have dbcontext included when adding a review to a book because of the performance. You also made me understand parts of DDD I hadnt realized before and my DDD libraries. This means I can write code in the DDD method that doesnt need access to the applications DbContext, as shown below. complex database work then I do it outside the entity class, either as a at System.String.Join(String separator, IEnumerable`1 values) To shorten our work, I used the ApplyConfigurationsFromAssembly command to apply entity mappings. libraries EfCore.GenericServices for calling DDD methods in the classes and EfCore.GenericBizRunner As you can see there is a middle ground where GenericServices cant do what is needed, but the code isnt complex enough to use GenericBizRunner. Personally, I will be using the IncludeThen version because it is less coding, but if I find there is a performance issue or something unusual, then I have the ability do fix the problem by adding specific EF Core code inside the entity class method. Initial Catalog=EShoppingTutorialDB;Integrated Security=True;Pooling=False", We can override repository virtual methods in order to customize repository behavior, Template Method Pattern. at GenericServices.Internal.Decoders.DecodedDto.FindMethodCtorByName(DecodeName nameInfo, List`1 listToScan, String errorString) Domain-Driven Design is an approach to software development that centers the development on programming a domain model that has a rich understanding of the processes and rules of a domain.

Article Copyright 2021 by Amanmohammad Toumaj, Throws Exception if Maximum price has been reached, or if no Order Item has been added to this Order, Throws Exception if Maximum price has been reached, Scans a given assembly for all types that implement, IEntityTypeConfiguration, and registers each one automatically, Data Source=localhost\\SQLEXPRESS; I have found that I use three different complicated. From what this article about I assume you are asking if I use GenericServices an my GenericBizRunner in the same project. public int ReviewId { get; set; } The question is, we have the Book loaded, but we dont For the next step, we add a domain model called OrderItem in Entities folder, which will hold data of every order item. Id love to get a bit more of information about your clients approach. The Order entity model checks some business rules and raises an BusinessRuleBrokenException (Custom exception defined in Shared Kernel Library) if any business rule has been broken. speed of development I was with the non-DDD approach, but now my code is much easier That because that library can: The code below shows an example of doing a test and returning a Status.