Intro to MediatR - Implementing CQRS and Mediator Patterns

[@georgesaeid7231]

This is the most elegant explanation of MediatR ever. Thank you.

[@IAmTimCorey]

You are welcome.

[@brandonpearman9218]

Been working with CQRS and mediatr for years now, and from my experience it generally makes complex systems more complex. The need for CQRS or mediatr is generally not needed but many devs use it everywhere because its a shiny new pattern.

[@IAmTimCorey]

I can see that. It is a pattern that really should be reserved for larger projects and specific circumstances.

[@brandonpearman9218]

@@madd5

[@ejenkins132]

It seems like one of the big benefits could be in unit testing. In many projects I work on, classes have a ton of dependencies that are injected through the controller. If we want to unit test one of these classes, we have to mock out each one of these dependencies and specify what each of their methods should return when called, which leads to a lot of boilerplate in the UTs. Using a single mediator in place of all those dependencies seems like it could remove a lot of that boilerplate. Of course, using a ton of dependencies in your classes also seems like a bad smell, so maybe that should be addressed prior to considering CQRS? :shrug:

[@brandonpearman9218]

@@ejenkins132 yeah, at first glance it does seem ut will be easier but working on both styles i dont notice the difference. Even in the case where you have a ton of extra dependencies it shouldnt be an issue in ut. There are a few solutions you could use. 1. Pass in null for dependencies not used(assuming you dont have null check because container does that). 2. Have a single location where you construct your class with default mocks but not stating what it returns. Then in each test set what the relevant dependencies return. 3. I built my own auto inject mocks in ut which was an idea iv been testing and it is working quite well because i never have to even consider a classes dependencies in ut (only what they should be returning for a given test)

[@brandonpearman9218]

@@ejenkins132 i was recently told to convert a certain project to mediatr. It took a small project and made it a big one. It over 10x the amount of files. the bloat is so disgusting and with the inability to goto a calling method, navigating this project and understanding what it does is so difficult now. But if I had to show you a single handler, you could say that its simple because it does one thing, and thats where the trap is. Simple when dealing with a handful of handlers.

[@Rondalaquanaynay]

Hey Tim, Like 7 months ago I finished an expensive bootcamp that.... taught me very little. I then signed up for your master class and completed it fully, A week after completing the masterclass got 2 very nice competing engineering offers. And here I am, today marks 1 month at my first engineering job AND my job happens to use Mediatr which you have now helped me understand perfectly. You da best. lol thanks again -Ron

[@IAmTimCorey]

Fantastic! Thanks for sharing.

[@bardus_hobus]

Tim, I want to say thank you for all your videos. I have finally landed my first job as a software developer, and I owe it in part to your amazing training. I am now going back through your videos to review some stuff they use (such as MediatR) for my continued education. Thank you so much for helping me reach my dream job!

[@IAmTimCorey]

Awesome! I am glad my content was so helpful. Congratulations on the new job!

[@RubenALopes]

I know that feeling, everytime something new comes up at work like this, I search Tim's channel and there it is: an extensive video explaining that topic like this one. Stay strong to keep learning and thanks Tim for making it a bit easier

[@sayedraminSadat]

Learned amazing staff today. Thank you Tim. I would love to see part 2 with advance MediatR implanted in complex application.

[@IAmTimCorey]

I will add it to the list. Thanks for the suggestion.

[@Keiktu]

@@IAmTimCorey Please do so! This video helped me out to have a very solid understanding of these patterns.

[@katekko1]

@@IAmTimCorey Waiting for it too

[@karthick8334]

@@IAmTimCorey Also do a video on MediatR Publish on top of this demo.

[@kpg7882]

@@IAmTimCorey How it's going? ;-)

[@roaba3581]

Easily the most understandable explanation I have seen. Totally worth to watch the 1,5 hours instead of a few shorter vids that don't really deliver the whole picture.

[@tomthelestaff-iamtimcorey7597]

Excellent point and thanks for sharing and spending the 1.5 hrs with Tim.

[@uchendukwe786]

Thank you, Tim. I love the way you take your time and explain details of concepts starting from scratch. You are a great instructor. Keep up the good work.

[@IAmTimCorey]

You are welcome.

[@wlopezm]

Such an excellent intro to explain Mediatr in the simplest way

[@IAmTimCorey]

Thank you!

[@Keiktu]

Mr. Corey. This video is pure gold!! Thank you very much for this video, I have been looking into learning CQRS and MediatR for a while.

[@stefan263]

Thanks for the effort putted, I appreciate! Also I am following you since more than 3 years. What you covered is great and the explanation as well. What I will state, is not related to this video but to the over use of this pattern. In my experience, 7 years now, I saw lately an over use of this pattern which leads to lots and lots of complexity which leads to technical debts and also bugs. Do not call another handler inside another one is bad design. If you are in the need of doing such thing then change your design. Make a XService for your XController, and let that service handling your flow. If you still want to use mediator, just inject it in the XService and call in the right order the handlers. Finally, the XMethod will be responsible to return/or not, the requested action. The benefits? Think about transactions, and much more, like SRP not violated, easy to test etc. To state that having many injected dependencies require mediator, is again, a naive approach. Why? Because we should fix the bad design of the code as easy as possible not by introducing a pattern which add heavy complexity. Also, if you are in a EDD structure, this will add another event pipeline which has to be maintained, upon many others like signalR, Masstransit with Rabbit etc. Maybe the reason of being too many dependencies injected in a class is due to the fact that SRP is violated and is doing too much, therefore it should being split by proper responsability. And much more can be said. Anyway, as last note, I just want to say that CQS which is somehow a CQRS, can be achieved without using the Mediator but just by separating responsabilities in Queries and Commands, at simple level speaking. Because real CQRS, implies a complex architecture/flow, like for example, Quries should have their own DB and so on.

[@antoniomarcos5664]

Hi, Tim. Great explanation! I have seen other developers getting a mess to explain clearly. How always your explanations bring us enlightenment. Thanks.

[@IAmTimCorey]

You are welcome.

[@masygoli2831]

It was one of the useable tech videos I've ever seen in KZbin with simple yet powerful teaching ability. Thanks a lot!

[@_rachid]

Currently I'm trying to learn how to build a .NET web api using Clean Architecture and I needed a cristal clear explanation of Mediator pattern, and thank God I found it on your youtube channel. I'm grateful to you Tim, thank you. Greetings from France.

[@IAmTimCorey]

I am glad it was helpful.

[@expertreviews1112]

Best video on MediatR! Tim your way of teaching is the BESTTT

[@IAmTimCorey]

Thank you!

[@runtimmytimer]

Great timing. I just started a project that uses MediatR. Pretty cool stuff. Nice job on the explanation as well. They've implemented a generic handler class GenericHandler that abstracts away all the handler implementations. Interesting approach.

[@tomthelestaff-iamtimcorey7597]

Thanks for sharing your real world experiences

[@fadidib8516]

Thx for showing both the record and the class way, easier to understand this way.

[@IAmTimCorey]

You are welcome.

[@MegaMatroc]

I just started with new project that uses Mediator library. This was whole new tool to me. So cool that you can bury business logic little deeper than what is usually in controller layer. Thank you for showing what is this pattern all about and how to implement it to project. Learned a lot and I feel like I'm able to understand this new project better now. Thank you very much for clear explanations. Much love

[@IAmTimCorey]

You are welcome.

[@DoubleDP007]

Hi Tim, the algorithm was useful this time round. So glad I found your channel. You are a natural born teacher, thanks for making things so easy to understand. Would be great if you could expand on this with some complexity including fluent validation, auto mapping and error handling in a clean architecture

[@IAmTimCorey]

Thanks for the suggestions.

[@delroymiller2630]

Tim, you did another excellent job breaking and explaining a topic that has challenged developers new to this tool and some of these concepts. Well done!

[@IAmTimCorey]

Thank you.

[@hyunbinpark3382]

This lecture was so perfect for me to understand how enterprise app works in general. Thanks a lot.

[@IAmTimCorey]

You are welcome.

[@vatansoni6439]

28:13 mediator 31:58 Query > IRequest 34:10 Handler > IRequestHandler

[@manuelapostol7664]

Thanks. Too much information when you only want to know about mediator

[@enfissione8297]

1.5 speed, very watchable and saves a lot of time.

[@androidsavior]

cant believe I've finally used mediator, it turns out it's so easy :) Thank you very much

[@IAmTimCorey]

You are welcome.

[@cymrucoder]

Incredibly useful video. We're refactoring an existing API at my work using the Mediator Pattern in the coming weeks, and this has introduced the topic to me so well! Keep up the amazing work.

[@IAmTimCorey]

Glad it was helpful!

[@ericwagner2307]

I loved the whiteboarding at the beginning with the gradual transition into code. Walking away from this one feeling very comfortable reviewing a codebase using MediatR. Thank you as always Tim!

[@IAmTimCorey]

You are welcome.

[@nicklebeezy]

Lessons learned in CQRS and MediatR; I would avoid having commands call other commands. Tim showed this on the Query side which in most cases is probably fine, albeit not usually necessary (IMO). However, in implementing CQRS for the first time it's really tempting to have commands call other commands which in my experience is an anti-pattern you want to avoid (say for instance you are trying to follow DRY or the S in SOLID). If you feel the need to do this, a better solution would be use Domain Events, which comes from Domain Driven Design. In my experience, if your requirements or business logic are complex enough to grow beyond CRUD operations, it's likely that you'll be reaching for CQRS and MediatR as a stepping stone to DDD anyways. I haven't seen many use cases that justify using CQRS that don't then lead into DDD in my opinion. Otherwise, great intro Tim. I do enjoy using CQRS and MediatR and it certainly can make life more convenient.

[@tomthelestaff-iamtimcorey7597]

Thanks for sharing from your experiences.

[@torrvic1156]

Thank you, thank you so much great teacher Tim Corey! Thanks to you I finally understood how to use this shotgun to kill the fly. Also learned that Queries are for Read operations and Commands are for Create, Update, Delete operations (both implement IRequest) and all of them are served by Handlers (which implement IRequestHandler). And with the help of MediatR it’s possible to invoke Handlers via appropriate Commands and Queries. Also I learned about .FromResult method to convert to Task (I struggled with it before).

[@IAmTimCorey]

You are welcome.

[@cotepatrice]

Nice stuff for someone who wants a quick dive in the Mediator pattern, CQRS and the MediatR tool. Thanks!

[@IAmTimCorey]

You are welcome.

[@LuisBragagnolo]

Tim, you are the best!!! You explain complicated topics very simple! Thanks!

[@IAmTimCorey]

You are welcome.

[@davidpeck7131]

Great content Tim & team, as always, on the Mediator/MediatR intro. Would love to see this expanded on part 2 (advanced), with pipeline concepts to touch error handling or logging.

[@IAmTimCorey]

I will add it to the list. Thanks for the suggestion.

[@Coeur85]

thank you time for the simple explanation , i watch a lot of videos about CQRS , none of them made sense till i watch yours :)

[@IAmTimCorey]

Glad to hear that!

[@bullheadrider]

Your explanation pattern is nothing but The best. God bless

[@IAmTimCorey]

Thank you!

[@alexsnegir1427]

Great video! Thanks, Tim! I'll be glad to see some DDD concepts in practice. Aggregates, Entities, Value Objects, etc. Also some Event Sourcing, too.

[@tomthelestaff-iamtimcorey7597]

Thanks for watching Alex.

[@David-rz4vc]

Yeah, would be nice to see some of those

[@vin2629]

I absoluely loved this. I have a clear understanding of CQRS and how to implement it using MediaR. Howeever CQRS pattern can be used in many other ways especially while using microservices. Please create a dedicated video on CQRS

[@IAmTimCorey]

Thanks for the suggestion. Please add it to the list on the suggestion site so others can vote on it as well: suggestions.iamtimcorey.com/

[@mehdihosseini2442]

Thank you for your excellent and practical training. Surprise us with part 2 on how to properly use CQRS, mediator and saga in microservice.

[@IAmTimCorey]

I will add it to the list. Thanks for the suggestion.

[@brianbaldos]

Simple and very easy to understand. Looking forward and wish for a separate video on how to unit test mediator handlers.

[@IAmTimCorey]

Thanks for the suggestion. Please add it to the list on the suggestion site so others can vote on it as well: suggestions.iamtimcorey.com/

[@Kattarhindusanatan22]

I would like to thank you for this great stuff.. I was afraid to watch such a big video but once I started time flies. And one more like for you haven't monetized the video it keeps the viewer focused. :) Thanks

[@IAmTimCorey]

You're very welcome!

[@blitzkidx]

Thanks Tim, one of the best tutorials i've ever seen!

[@IAmTimCorey]

You are welcome.

[@misterwoody_]

Many thanks Tim. Finally a video that covered reducing the dependency injection overload I was interested in, and how to put controllers on a diet. All the best.

[@IAmTimCorey]

Glad it was helpful!

[@cristiancalichio5335]

Thanks Tim, very good explanation and introduction to the topic. It helped me a lot and was very concise! Greetings from Argentina!!!

[@IAmTimCorey]

Glad it was helpful!

[@es7729]

This video was awesome! I've to use this in my current project, never used it before. Now I know how and what! Thanks!

[@IAmTimCorey]

You are welcome.

[@nadervaghari51]

wow! I really enjoyed watching this wonderful course. I appreciate the way you teaching and rectifying the problems. Thanks Tim 👍🙏

[@IAmTimCorey]

Glad you enjoyed it!

[@kartheeknandini3767]

Long waiting ended. I am waiting for this. Thank you Tim

[@tomthelestaff-iamtimcorey7597]

Thanks for hanging in there with us!

[@anrodse]

Great video again. Thank you very much for all this work. Just two points that disturb me: 42:00 Create a new class (DependencyInjection?) at DemoLibrary project to extend IServiceCollection, adding a new method like AddDemoLibrary(this IServiceCollection services). Call services.AddMediatR() from there, using its own assembly (ie. DemoLibrary). 1:13:00 I would use InsertPersonCommand class as parameter. That way, people don't have to set an id to create a new person. An id which has no use anyway.

[@shahzshafie]

i really enjoy this video.. simple to follow. Kudos Tim!! I (and i think many of the comments down below including myself) would love to learn more advance usage of these patterns, more so gearing towards the real enterprise systems. Thanks man... you are awesome!

[@IAmTimCorey]

Glad it was helpful!

[@sbeasley1120]

Loved the content. I’ve been using MediatR for over a year now and I learned something new today. My only critique is you mentioned CQRS at the beginning then you lumped you commands and queries into the same api. And that doesn’t allow them to be independently scaled. I know it really wasn’t the point of this video. So a video on Behaviors and splitting up command and queries would be awesome

[@pilotboba]

Yes, I would argue this isn't an example of CQRS as described by Greg Yong, because it doesn't have separate read and write models. But, this is a good example of CQS which has clearly separated the commands from the queries. Queries shouldn't have any side effects... you should be able to make the same query all day, and they don't change anything. While commands mutate things or have side effects.

[@tomthelestaff-iamtimcorey7597]

I noted your recommendation by adding it to Tim's list of possible future topics, thanks.

[@keyranjoshi10]

I am really appreciate your efforts and time to make this video. Very detail and easy to understand. 👏👏👏

[@IAmTimCorey]

Glad it was helpful!

[@Kyogunaik]

With all of your videos, One day I’ll become a solution architect for sure😇

[@IAmTimCorey]

Best wishes on your journey.

[@Kyogunaik]

@@IAmTimCorey thank you so much 😊

[@DrCox-xx8tu]

Nice beginner tutorial for MediatR. Although I already was familiar with the things you showed, I really appreciate your work Tim. Could you maybe do a more advanced video on the additional features MediatR offers? For example validation, logging, exception-handling, ...

[@tomthelestaff-iamtimcorey7597]

I noted your recommendation by adding it to Tim's list of possible future topics, thanks.

[@thegaribovv]

Tim, I really appreciate your tutorials quality

[@IAmTimCorey]

Thanks!

[@joeyvico]

This was a master tutorial Tim. Excellent work. Thank you so much

[@IAmTimCorey]

Glad you enjoyed it!

[@junianohjj4602]

Hi Tim, great tutorial. I have been using MediatR and i like how my project is organized, especially simple API Controller routes. However I prefer having my Queries/Commands on same file with their corresponding Handlers for an easier lookup. Adding FluentValidation to MediatR makes it more powerful with how and when do handlers gets hit.

[@IAmTimCorey]

Thanks for sharing.

[@David-rz4vc]

I agree, having the handler be an internal class within the query or command files is useful for easy lookups. I like to have mine organized in features folders.

[@GrigoryZhadko]

Hi. How do you pass information about User (ClaimsPrincipal) or HttpContext info to mediator? The original request class doesn't contain such information. Do you create additional class which looks almost the same as original request file but with additional User property?

[@craigfreeman8225]

Amazing that I was just watching a video on Onion architecture and trying to figure out why the application layer in the example used MediatR. Cant wait to watch this :D

[@IAmTimCorey]

Great!

[@ВасильЗауличний-у2е]

Great video. Very easy and clear explanation of the CQRS and Mediator patterns! Just the practical stuff. Very nice point about balance as sometimes people tend to hyperbolize patterns :)

[@IAmTimCorey]

Thank you!

[@RaihanTaher]

Thanks Tim for explaining things so clearly. You made the learning experience easy. Keep up the good work.

[@IAmTimCorey]

You are welcome.

[@vrajeshbadgujar]

Thanks Tim, for another great explanation! please cover tutorial for MediatR pipeline behavior.

[@IAmTimCorey]

You are welcome.

[@hannimedable]

Wow, that for sure will move some plans from the evening!

[@IAmTimCorey]

Enjoy!

[@hannimedable]

@@IAmTimCorey hope you also have something about event sourcing on your list :)

[@yossrikhalil9551]

I would love to see some event sourcing tutorial as well

[@FinallHit]

0:00 - Intro 1:01 - What is CQRS 3:49 - What is Mediator 9:00 - Mediator Pattern 12:00 - Create BlazorUI app 13:24 - Create DemoLibrary Class Library 15:25 - When should i implement MediatR? 19:22 - Setting up DataAccess class 25:10 - Setting up BlazorUI app 28:18 - Adding MediatR Package 28:48 - Build out MediatR Setup 29:08 - Setting up Queries 30:08 - Difference between Class and Record 30:51 - Setting up GetAll Query 33:33 - Setting up GetAll Handler 38:30 - Configure StartUp (BlazorUI) 43:21 - Inject and use MediatR in razor page 49:30 - Create DemoApi Web API 50:44 - Configure StartUp 51:52 - Create Controller 52:58 - Inject MediatR 53:26 - Implement HttpGet all 54:16 - Run DemoApi 56:27 - Setting up GetById Query 58:05 - Setting up GetById Handler 1:03:11 - Implement HttpGet by Id 1:04:28 - Run DemoApi 1:05:25 - Setting up Insert Command 1:08:55 - Setting up Insert Handler 1:10:34 - Implement HttpPost 1:12:38 - Run DemoApi 1:13:59 - Recap Thanks for the awesome content! Learned alot, Cheers!

[@IAmTimCorey]

Thank you!

[@DerekWelton]

Great video Tim as always. I would recommend though that it wouldn't be best practice to call queries/commands within handlers as it will go through the mediator pipeline again calling all the behaviors causing more overhead (unless you purposely want it to go through that pipeline again)

[@idowutosinmichael9120]

I dont understand this please

[@PradeepSingh-ly5oq]

Thank you Tim for creating such a wonderful Video.

[@IAmTimCorey]

You are welcome.

[@thehamzajunaid]

Thankyou so much. Covered so many aspects and was very easy to grasp.

[@IAmTimCorey]

You are welcome!

[@parsamh78]

That's just what I need. Thanks a lot Mr. Corey ❤

[@IAmTimCorey]

I am glad it was helpful.

[@pianoman1973]

Great and easy to understand presentation of the topic !

[@IAmTimCorey]

Thanks!

[@nbhariyani]

Thanks, Tim. Very nice detailed explanation. Other than this topic would like to know few things. 1) Which VS version you have used. 2) What Intellisense has enabled you in the VS. 3) What are the best and useful shortcuts for c# developers you can recommend.

[@IAmTimCorey]

I use Visual Studio 2019 Community Edition. The Intellisense I use is standard from Microsoft. I also don't use custom extensions (except one for resizing the fonts for better visualization on video). As for shortcuts, this video might help: kzbin.info/www/bejne/p6eZi5miqsp0ibs

[@paulpitchford]

This really joined the dots up for me. Thank you.

[@IAmTimCorey]

You are welcome.

[@andywalter7426]

I would still love to see source generators covered. Because since reflection is too slow for webassembly and webassembly is getting more common for blazor, then source generators would be a good solution to avoid the performance penalty of reflection.

[@IAmTimCorey]

I will add it to the list. Thanks for the suggestion.

[@bohuang3122]

It's a wonderful teaching video. Thank for the sharing!

[@IAmTimCorey]

You are welcome.

[@meryemaydn8615]

You are amazing Tim. Thanks a lot to you. You save me from a big deal. take care please. I will need your videos again :)

[@IAmTimCorey]

I am glad my content has been helpful.

[@viktoralferov2874]

Hi, My favourite package - MediatR. It allows you to make less coupled programm. Thumb Up I also use aliasing: using TRequest = RequestType using TResponse = ResponseType class SomeRequest: IRH + FluentValidation

[@tomthelestaff-iamtimcorey7597]

Thanks for the recommendations

[@viktoralferov2874]

@@tomthelestaff-iamtimcorey7597 like this: namespace ... { using Request = RequestCommand; using Response = RequestCommand.Result; [DataContract] public class RequestCommand : IRequest { public string SomeProperty { get; set; } public class Validator : AbstractValidator { public Validator() { RuleFor(...) } } public class Handler : IRequestHandler { public async Task Handle(Request request, CancellationToken cancellationToken) { ... } } public class Result { public string SomeProperty { get; set; } } } } Sorry for code. If I should not do it here - just give me know that. Thank You (Tim).

[@goodmanshawnhuang]

wah, another amazing masterpiece from you Tim, thank you so much for sharing it, you are just the best!

[@IAmTimCorey]

You are welcome.

[@2005bgva]

Hi Tim, thanks for this video, it was very interesting. Maybe a idea for future videos: you could do a video of how to implement Mediator pattern from 0.

[@IAmTimCorey]

Thanks for the suggestion. Please add it to the list on the suggestion site so others can vote on it as well: suggestions.iamtimcorey.com/

[@leosouza1520]

Excelente explanation about the mediator pattern.

[@IAmTimCorey]

Thanks!

[@craigrichards5472]

Great walkthrough, your demo of Records was perfect 👍

[@IAmTimCorey]

Glad you liked it!

[@martaskarbek6261]

I like the way You are communicating knowledge. I would love to watch some intro into the factory pattern (seems easy, but is a bit tricky in a way) and multithreading if You ever make one ;)

[@IAmTimCorey]

I did cover SOLID (the Dependency Inversion Principle video covered a VERY simple factory design - I'll be doing a specific factory pattern video at some point) and I covered async/await (and advanced async), which handles most multithreading needs.

[@mofidmoghimi581]

Thanks Tim. It's very useful. Please make a video about event sourcing.

[@tomthelestaff-iamtimcorey7597]

Thank you. I have added this to Tim's list of possible future topics.

[@ItsAllAboutMusic92]

Great Video! Thanks for that! Please make another one with more advanced topics!

[@IAmTimCorey]

I will add it to the list. Thanks for the suggestion.

[@mortezanejat8707]

u actually make OUR life easier.

[@IAmTimCorey]

Great!

[@timnguyen8190]

Thank you Tim, your explanation is great! Love it!

[@IAmTimCorey]

You are welcome.

[@JoeXhungary]

Hi Tim! Thanks for all your great videos! A few days ago, I met again with Reactive Extensions. I love it's way. Do you plan a video about Rx? (I'm interested in especially ReactiveUI)

[@nnamacha]

Simply and Clear. Thanks Tim.

[@IAmTimCorey]

You are welcome.

[@themagecan]

Thanx Tim Thats Great Video Please continue This series 🙏

[@IAmTimCorey]

You are welcome.

[@abdulrahmanalenezi620]

Man you ARE THE BEST!! THANKS FOR THE AMAZING COURSE

[@IAmTimCorey]

You are welcome.

[@RAZOR3181]

Hey TIM!!! That is a great video and helpful for Enterprise Applications...Thanks.

[@tomthelestaff-iamtimcorey7597]

Thanks for watching

[@facundonavarro7895]

Would you recommend to use Dtos instead sending the model directly to the UI from the controller using Automapper to map them?? Excellent explanation of the tool.

[@learner8084]

Thank you very much, Tim. I find this video excellent.

[@IAmTimCorey]

You are welcome.

[@alinazar7998]

thanks for this very good intro to MediatR!

[@IAmTimCorey]

You are welcome.

[@andrea-wc7fd]

Thank you very much from Argentina!

[@IAmTimCorey]

You are welcome!

[@subbur4439]

Excellent video explains the concept very clearly

[@IAmTimCorey]

Glad it was helpful!

[@alickcampbell8915]

Great introductory video!

[@IAmTimCorey]

Thanks!

[@suchoss4770]

Hello Tim. Great explanation of this topics. Thanks for that. If I may have an additional question - and I mean it seriously - to this topic. I do not want to start any flame :). From what I just saw, it seems to me, that Mediator pattern leads to a class explosion (Queries, Handlers). Also I do not see hiding dependencies as a benefit. So my question is: - Is there some pivot point where Mediator starts to be beneficial? Or is there something what I can do with this pattern, what is not (easily) possible with just dependency injection? Thanks!

[@vladimir-savikj]

Hello Tim, amazing tutorial and coverage of MediatR. You mentioned that it is suitable for bigger and more complex applications. I would like to share my opinion with you and the rest of the comment section. In a complex real-world application, let's say we have 100 models, on average with 5 queries/commands. We would have 500 files of queries/commands. On the other hand each of them would have a handler, so that equals to 1000 files. Personally, I wouldn't swim in that sea. For example, isn't it a better approach, to have RepositoryManager with lazy loaded 100 repositories(with all CRUD operations, accordingly). That way, we would have only 100 files. So, for instance, service A needs Repository B,C and D, it would have the similar benefits as MediatR with RepositoryManager(without directly depending on them). Thank you :)

[@IAmTimCorey]

Thanks for sharing!

[@vladimir-savikj]

@@IAmTimCorey I would like to hear your opinion on this. Thank you so much 😁

[@wertrager]

Excellent modern app architecture

[@IAmTimCorey]

Thanks!

[@GrigoryZhadko]

Hello. Thank you for a great video. Could you please explain the proper way to pass additional information about ClaimsPrincipal to mediatR is? E.g., in your example, there is a method Post([FromBody] PersonModel value) in PersonController. What if I use Authentication and have User property in my controller, which I also need to pass to InsertPersonHandler. Should I extend the existing PersonModel (and probably call it PersonModelRequest) with User property, which should be initialized in the controller? But all the elegance of MediatR approach will be lost.

[@WojtaZy1996]

You can put the handler in the same file as the query record to cut the number of files. The handler is easier to find then too.

[@Ahmad_Hamdy_Hamdeen]

A lot of thanks Tim that is an amazing explanation. 👌👍😘

[@IAmTimCorey]

You are welcome.

[@alirezahabibi-i9r]

at the first of the video i said oh my god what's going on 🤨but your explanations made things clear 👌 thanks

[@IAmTimCorey]

You are welcome.

[@joergenvig]

I think Mediator-pattern makes debugging mutch more complex. Change my mind :-)

[@sunila6539]

Great explanation as always. Keep up the good work

[@tomthelestaff-iamtimcorey7597]

Thanks for watching!

[@huntersMoon01]

very nice... clear and to the point of subject

[@IAmTimCorey]

Thanks!

[@anurag0304]

"Wow, watching your video was like going from trying to understand rocket science to finally getting why the chicken crossed the road! Thanks for decoding the Matrix for us 😄🚀🐔

[@IAmTimCorey]

I am glad it was helpful.

[@travelbuddy4000]

You mentioned using Singleton for insertions is bad. Do you have a video explaining why, that would really help me understand it