How To Use Domain-Driven Design In Clean Architecture 

Master the Clean Architecture: bit.ly/3PupkOJ

Honestly. After few weeks of learning fundamentals of DDD, watching conferences, tutorials, reading blogs and articles about how and what to refactor, why this or that way, when and what set to private/internal or leave public I can say with 100% sure - this is the best explained video concerning this topic. Now its going to be easier for me to refactor my learning projects from anemic to rich model and be motivated to write code again :)

You have a gift for comprehensive and precise communication without unnecessary filler material.

I really like how you explain complex concepts and designs in a such simple way. Extra butter to your videos is that examples are not "dead" - you try showing things on cases that are close to real domains. No "Foo" and "Bar" involved, which is really great!

Milan, needless to say that this was once again a great and awesome video :) Great work picking a somehow complex topic and make it look like a simple action without being lost at the definition hell of DDD :)

Honestly, this is the first video that I fully understand from this channel. I know that the owner of the channel is a high-level person, but the videos he shows are always short. It shows the problem quickly, but in this video I got a very high benefit. I hope the channel owner makes videos like this in the future . in end thanks Milan 😎🎯👨‍💻

Milan, another great and useful video! I must say you choose video topics wisely and bringing quality content. Would love to see more on domain driven design concepts with the examples.

A friend of mine recommended your channel and your videos are awesome! Keep up with the good work man!!

Awesome! I really liked the fact that you didn't just bring a finished solution and showed it, but rather explained the process step-by-step and the reasonings for each decision. That's a clever way of teaching this topic. I'll try to binge-watch your videos about DDD as this is a new subject for me.

I liked your step-by-step approach and your explanations about postponed decisions.

Really nice topic and great content! As someone working in education, I appreciate your effort to give such nice practical examples.

Great explanation! Thanks for your efforts to create this kind of content! I learned a lot from this video.

Great video with proper duration for the topic! Excellent example of transforming anemic to rich domain model. Thanks!

Thank you very much Milan. started getting good exposure into clean architecture and DDD. good luck!

Great content, keep it up. I would like to see a video on separating your domain via bounded contexts and how that would work with EF.

Great video thanks! Can't wait for the next one to see how you gonna handle unanswered question with sending the email. As you told me on previous video probably it's going to be with mediatr publish notification. Keep up the great work!

Lucky I came across this video...... and finally got understanding what we were doing wrong. Thanks for the excellent content.

i think this is the best explanation so far about how to design a rich domain, Thank you Milan. And i am really waiting for a series in which you start building a project from scratch to see the best practices of design and layers implementation with you, Thank you again for your efforts❤

I am amazed. Thank you Milan.

Very well put video !

Great job, bro👍👍 Waiting for the next videos

Thanks Milan, You are perfect as always

Found you on LinkedIn. Love design related videos you're posting!!

Nice video! Looking forward to the next one.

Insted of returning null, you can use the keyword "default". And thank you for your work Milan :-) you are doing good !

Beautiful content, you have helped me improve aspects of my domain implementation. Please continue to release more content Milan, this type of content motivates me a lot in my professional career. Thank you very much for your contribution!

Great tutorial, keep it up.

Another excellent video Milan. Watching you do the migration piece by piece is a really easy way to understand the differences between an anemic and rich data model. Which is the next video you eluded to? Domain events or outbox?

A definitive *bold like* for this one! One thing that bothers me in this rich domain implementation, and not explicitly mentioned in video, - is that the time retrieval logic moved from the application layer to the domain one. In this example the domain just takes UTC from system clocks, but it may not be the domain's responsibility (and authority!) to act this way. The most suited implementation of a time provider may depend on a specific environment, but higher layers have no control over it now.

I would recommend reading about DDD starting from Von Vernon's "red" book and then reading Eric Evans's book.

Thanks for great video, Milan! 15:07 Since the actual object being returned above is still a List, a caller may cast the result to a List and then add or delete an invitation. Because of this, you should use read-only wrapper by calling .AsReadOnly()

Great video !

Hi Milan, love your videos. I am learning a lot. I would like you to consider changing a setting in your Visual Studio. In Tools -> Options -> Projects and Solutions, select "Track Active Item in Solution Explorer". I suggest this because you move so fast from one class to another. This would help some of the viewers to better identify in which class you are working. Thanks and keep up with the good work.

I found your content first by LinkedIn, and I really want to say that you are an amazing teacher.

Before going to bed I preferred to watch this video instead of listening to music 😍

Great job and another great video.

Thanks for the wonderful videos you have posted on RU-vid. I'm working on a large-scale WPF application, and I've decided to do a DDD design for obvious reasons. However, I struggle with limited contexts and some potential circular references. Let me clarify: I'm working on an application that will measure traffic lights in a production process. The app will also include some serial number generation and other business related stuff. due to size and complexity, I decided to have three projects in the domain layer. Domain.Shared (base classes for Aggregate, ValueObject, Result ...) Domain.Measurement (logic for calculating product measurement results) Domain.SerialPort (Logic for SerialPort, where I specify specifics and client commands). Domain.SerialPort is boundedContext because the user must specify these settings in the user interface, and there are constant changes and versions of the product. The problem I have is that I want to specify a two-way property in EF. if i want to do this i need a field from Domain.Measurment to Domain.Products and a field from Domain.Products to Domainain.Measurment which creates a circular reference between projects. Another option I have is to inherit the entities in the persistence layer and just add the two-way fields there. what would your suggestion be?

Amazing!!!

Excellent

Thank you Sir! Amazing:))

Wow...Awesome...just loved it...please keep it up for the community who encourage to learn....please make a video on productivity shortcut on visual studio if you could so that everyone can get more benefits out of it.

Awesome!

I thoroughly enjoyed your content and wish I had discovered it a year ago. Your explanation of concepts is both precise and on point. My only suggestion is to consider developing a structured path that guides learners from creating projects from scratch to a level where they can confidently produce a fully functional application, perhaps through a series of 10 videos progressing from beginner to advanced levels.

Hi Milan, you have truly great skills to deliver somewhat complex content in clear and concise way:) I've got two question (unless you already covered those in another video): 1. What do you think about abstracting away dependency on DateTime in your domail model (e.g. to make testability easier)? 2. What is your opinion on returning types from your methods representing commands (e.g. Invite) instead of keeping return type void and follow CQS.

Thanks for great content. Saga can be used for db saving and sending email transactions. Masstransit would be a great content to cover. I really appreciate the concise and excellent way of explaining.

Good! wasn't it better to call AsReadOnly method to return IReadOnlyCollection. This way (not using this method) clients may simply cast the collection as List and modify it

Rule of thumb: whenever you write a couple of lines that all do obj.Property= or obj.DoSomething() - consider moving that code into the implementation of the object - especially if you do the same or very similar changes elsewhere. Certainly, a property like NumberOfAttendess (which is redundant as it is equal to the count of the list) must never be writeable from outside.

Awesome ⚡⚡⚡⚡👍👍

Thank you for this wonderful video showing step by step, moving logic from Command Handlers to Entities itself. I have a query on implementing the same for Database First approach where the DB is already created for us. In such cases,we auto generate the entities using Scaffold-DbContext command and every time there is change in DB design, the entities are auto generated. How to tackle those situations? Do we put all domain logic in separate partial classes? Thanks again for this series.. I have been using N-Tier architecture for so long that this is a whole new fresh air of learning and I am very happy to be able to learn this new architecture.

very brilliant Video...

Another step could be encapsulation of the wole collection into an "Attendees" class. I'm curiouse about a video on Domain Services, maybe with the distintion about impure and pure domain services. 👍

Thanks for the video. Is there any added value of using a static factory instead of new Gathering()? The switch/case statement can be a method of the Gathering entity that is called on the constructor as part of the minimum validations in order to build a valid Gathering.

NIce content, await NextVideoAsync(). For the email part (hope this is not an overkill), you would probably use the Mediatr notification and publish to something that is not on the main thread and might not be awaitable like hangfire or an In Memory Background Service to handle retries even if it fails.

Hi, just a dev tip: when you were replacing that constructor parameter invititationsValidBeforeInHours, you could do a multi-cursor there with Ctrl+D 2x times for the 3 occurences and not 3x times navigating with a mouse ;-) but maybe you already know this after 9months of publication of this video

perfect

Hey Milan, great content! thanks for sharing. I've seen before that instead of having the repository independent of the unit of work (as you do on your video) there are people that implement it in a way that the unit of work contains the repositories such as: _unitOfWork.PersonRepository.AddPerson(person) Any thoughts on that? just curious! Thanks!

Great tutorial and awesome channel ! @11:09 why do you leave the guid as a constructor parameter ? Is that a bad practise to generate the guid directly in the constructor itself?

Hi great video ! I have two noobie question : 1) at 9:32 , in the SendInvitationCommandHandler, you create an invitation then you add it to the gathering.Invitations list (line 63) then add the invitation in its repo then SaveChanges(). What is the purpose of doing both? Cant we just add the invitation to the repository and SaveChanges OR add the invitation to the gathering.Invitations list and just SaveChanges since EF is tracking? 2) at 24:00 cant we just keep List Attendees but give it a private set? Instead of making it a ReadOnlyCollection and create whole new field private? Ty so much in advance!

great video, I want to know what's the alternative for returning null, did you make a video for that?

An excellent video. What do you think about the opinion that domain driven design works well only if we know all of the project's business logic from the beginning and that this rarely happens in the real world? And some folks claim in such situation it is better to use the more old school multi layer architecture with presentation, business and database layers and annemic models. It would be great if you can shoot a video about comparing the pros and cons of both.

Great video, thank you. One question to 24:30. Shouldn't logic defining rules for calculating whether invitation expired be considered as some kind of business logic and thus belong to Application instead of Domain layer?

I prefer when business logic is everywhere, yet clearly identified. For example, the presentation layer could know the format of a US zip code. I prefer when layers are not distinct projects (file). A class could be able to talk to DB via basic interface eg. DAO. Well I also like to go for twho parts: Backend (endpoints) and frontend (CSS+HTML+Javascript).

I think, for the case of "sendEmail" error, the best approach would be put the email in a queue or in a table to some cron job get end send it.

Thanks for the videos and effort - Just a comment -The video is supposed to cover the domain but you started with the application and commands - Also, it could be more helpful if you create the domain entities step by step or at least a couple of them. Thank you.

Milan, what is in your opinion the advantage of having a static factory method instead of implementing the full factory pattern ?

Nice video, self-explanatory. In this case, business logic is encapsulated in the domain model and it's not dealing with DB but let's assume that business logic needs some interaction with DB, meaning if-else would call different DB logic (repository). By design, we can't inject a repository to get needed data but how would you approach DB interactions from your domain model?

Great video, thanks, the short question, why do we use method name Gathering.SendInventation considering the fact that method does not perform any 'sending' logic and just add a newly created Inventation instance to the Gathering?

Hi Milan, Is there a separate video for the Application project?

When you are doing data validation video, could you take an example of the nature of "there should be no 2 members with the same name\email"? I'm interested in how you are going to avoid the data racing condition, when there are 2 simultaneous requests to create a user with the same name. I understand how the optimistic concurrency works on the level of an entity, but what are you going to do when it is not practical to aggregate all the data necessary for the validation in one entity?

I found you via LinkedIn, nice videos for sure, keep the good work

Do you have a link with the book you mentioned about DDD ?

Which keyboard do you use? I really like the sound of it. Blue switches?

For the gathering, you can just use a record. No need for private setters or separate ctors.

Good explanation I am following your tutorial but I have one question you put send invitation inside gathering class isnt it against S of Solid principles ? because our class is not only responsible for create gathering but also it is sending invitation ?

How would you go about translation to different languages? I mean mostly static error messages etc.

Hi Milan, Is there a way to restrict private fields assignment in certain cases within the model? Context: Hypothetically if I save age and birthday both in db anytime I update birthday it should update the age. But anyone within the model can still set those fields by directly assigning values to the private fields.

Hi ! I read that ctor should be private in model to avoid creating anywhere except in the model himself. But how do you convert object coming from databse (objectDTO) to the object domain model without a public constructor ? I could use create, but it doesn't work with the ID property which shouldn't be changed

I see return Unit.value where is that. Can't see it in the class anywhere

Hi, Milan I'm not sure, that changing the Invitation's properties inside of the gathering is a good way because it looks like a side-effect. I think, that the Gathering class should only have the possibility to check the expiration and AddAttendee(attendee) method

Might be a really really dumb question, however, let's suppose I want a User Crud, in this more spefic scenario I want to create an User account. Then should the Controller instantiate a User (by using the Controller) and then pass the User object to the repository and have faith on the User validation since an error wasn't thrown? Also, what do you think of Services? When should we create them? I've heard of some people that Services should be an action (verb) that makes use of different domain objects.

Isn't writing logic in the entity class against solid's s principle? Doesn't it make more sense to apply the factory pattern in a separate place?

Do you use async every time you call db operations even if it only returns 1 row of data or 1 column?

Hi Milan, In this video you created a static method responsible for creating a gathering entity. How would you create the gathering entity when getting the records from db using Dapper. If I am not mistaken the Dapper mapper will not be able to create the entity right?

Now that's the true DDD

Which program are you using for drawing class diagram? 1:10

@Milan Was reviweing this vídeo and I need to ask. What tool you use to make the class diagram in 1:20?🤣 Thank you

I'd be interested in if you are going to raise the issue of, when you are submitting updates, to not allow an invalid domain entity to be constructed - ie, not applying updated values to an entity unless you can first validate that the new values won't put the entity into an invalid state especially when dealing with complex aggregate entities.

are both the domain model and entity model (EFCore model) same? is there any difference in domain model and entity? generally my entities are suffixed with Entity (InvitationEntity) and domain without any suffix.

What is the problem of the logic inside de constructor or inside of the static factory method create? Why one approach is better than the other?

In minute 15:33 why would you add the invitation to the _invitations list if you already add it in the repository afterwards?

At 22:10 why do we move invitation accept logic to the gathering entity? In my mind accepting an invitation is not responsibility of gathering object

Thanks Milan. Shouldn't the commands and queries live in Domain and theirs handlers live in Application? Is there any wrong with this approach?

What do you think about defining repository interface in the Domain layer?

I couldn't understand why did you something like that with Lists (in 15:18) I think that EF core can handle all of them... or may be you did this because you wanted to use other ORMs like dapper? also i dindn't like adding SendInvitation into Entity... i think it's a buisness rule, and I have to implement that on application layer. note that: i'm not a native guy so some times i can't translate my right meaning i'm Sorry if I was disrespectful, I like your videos very much

Thanks for the video. What is the best way to avoid god objects in that kind of architecture? What if I have a domain entity that used in dozens of different scenarios? Isn't it too much for one class to contains the whole business logic related to the entity? How would you segregate and handle with domain entities which have a lot of fields, methods, and different constructors?

Can anyone help me create that project structure where inside solution we will be having src folder and and all the project inside that src?

Good video! But one mistake. Keep a private parameterless construct in every entity for serialization and EF query mapping.

How do you handle domain objects and persistence? Because a domain object's structure may not be suitable for relational DB persistence.

Hi Milan, could you recommend me some books about clean architecture and cqrs?

Hi Milan, Thanks for this awesome video. By the way, I want to mention that your code heavily violates SRP and OCP.