ASP.NET Core - Service Scope - Singleton vs Scoped vs Transient

welcome to another episode today we're going to be discussing a service scopes and first of all I'd like to thank all my subscribers and viewers I'm on 600 now I'm steadily approaching a thousand which is gonna be my next goal and just wanted to say thank you for sticking around if you have if you're new welcome subscribe like and hopefully you'll enjoy the content so I've set up this little application this is going to be available on github to play around with and download but basically the whole premise of it is I have three services here once transient once scoped and one is singleton service and today we are going to understand what is the difference between adding a transient adding a scoped and adding a singleton service to our dependency injection container which is the I service collection okay so the setup for this project is basically I have this AI service interface and all I want my AI service implementation to do is to return a string which is going to be a generator good and I have three services so the first one let's take a look at this they actually look all pretty much the same they have an interface that is basically represents the registration type and all they're doing they have a constructor where once the object or the implementation is created that's when we create a unique unique grid and when we call the get good function that's when we return the good okay and this is pretty much the same for all three services the reason they have different names is just so I can retrieve a specific one and still know which one it is here so all these three services have been a registered transient service was registered as transient scope the scope and singleton is single right so I now have my home controller where I essentially inject these services and then I have three pages where I go ahead and try to use these services okay so let's go ahead launch our application at the moment we're on the index page and the index page is the one which renders as the singleton good alright so I also have in my project if I look on the index page and on the scope a a scout page I also render a partial we're in the partial view what I do is I essentially they again they all look the same but what I do is I inject that respective service into the partial view and I render the good from there as well okay so this big ID here this is what I pass into the model as a model to the view and this is what I pass in as an injection in the partial view all right so if I go to the index page where I render my partial view I'm not actually passing any data into it I am injecting the service into the partial view okay so let's go ahead and take a look what we get so on the single took page if I stretch this out a little bit we can see that the gooood on the page is exactly the same okay if we refresh the page however we try to refresh it the GUI doesn't change what does this mean in terms of the service all right so if we go to the implementation of the service and this good that is returned from this function doesn't change that means that the service remains exactly the same throughout the lifetime of the application okay so it basically it doesn't matter what you do as long as your application doesn't shut down your service the instance this object that you have created will not change will not get disposed off and will remain the same okay so the primary uses for it is having stuff like cashing services and maybe some global configuration which won't change and you just want that same object you just want to inject it and you want it you want it to do exactly the same thing which is again we're good for business rules which might be objects with like collections of functions which might not have too much state at that point but if you want to persist some state throughout the lifetime of the application again this singleton service can be really good and also there is an H t-tau you might want to put HTTP clients into your singleton services and the reason why I left a link here it's a nice little blog article which describes how HTTP clients in c-sharp work so you might want to go check that out okay now this singleton service is something that is created once and it's just sort of it's there and when you call upon it you get the same instance doesn't matter where you inject it in your application it's always the same moving on to the scoped one you can see that in the partial and in the gooood we get the same IDs but if we refresh the page the what's called the partials change but they're still the same this tells us that whenever we use a scoped service for a request the ID will remain the same but if you issue another request the ID will change this means a new object a new instance is created every time you make a request so what is this useful for it to be honest I have not used a scoped service I haven't gone and created something that actually required a scoped service I always either lend towards a singleton or a transient but AI could imagine if I would want to use a scope service it be something to persist as a state through the application or request the way I'd imagine it is like a bucket which basically gets created at the start of a request if it's a long-winded request and you need to sort of maybe perform an atomic operation you would slowly fill fill up this bucket throughout the services that get called in your application and then by the end of it it will get disposed okay so if you think you need some sort of that functionality where you wanna have some state that will persist and you want to call upon it from different parts of the application in a request then scoped is your choice away all right and moving on to transient we can see that the grid on the page is different from the partial view and if we refresh again they are both different so the primary reason for this is that anytime we extract a service that is a transient service from our dependency injection container that instance is always fresh and new remember that constructors get called when objects get created and we assign this good inside the constructor okay where would you want to have a new object every single time throughout your application well it's stuff that depends on state that's somewhere else all right so when you are basically outsourcing your States so like a database access you're basically you have a connection and you want to sever it you basically you spin up a new instance you create a connection and then you sever it and you get disposed of it by Alexis again you have a connection to a file you have this stream you have all this memory accumulating you want to sort of create that bubble and you want to throw it away at the end of it services that should be disposed of their state this is really kind of the underlying principle of the transient service see you you want some state or you have some connection that you just want to get make sure you get rid of remember that these services dotnet core takes care of basically disposing of them so what I mean by that is usually when you create a class you'd have to do something like implement from I disposable and then you need to create your own what's it called dispose function so if we implement this interface you'd have to basically do something like dispose of your goods so you'd have to say no here or if you have a connection you'd have to like close connection safely and just remember that if you have a transient or a scope whenever you're disposing of your state and your service dot net core takes care of that for you and the last point that I had on there yeah it's just if you need a fresh instance of an object every single time so let's say you have an object that has some state and depending on which functions you call in that object the state will change but if you reuse try to reuse that state and call those functions again basically stuff will stop start to break so you need a fresh instance every single time so that's when you want to opt in for a transient service so hopefully you enjoyed this nice short little video and learn something new again if you liked this video like subscribe turn on notifications if you have any questions leave them in the comments if you want to make any video requests you can leave that in the comment as well but for now thanks for watching hopefully I'll see you in my other episodes have a good day

Channel: Raw Coding

Views: 23,152

Keywords: dotnet, dotnet core, dotnet core tutorial, dotnet core guide, .net, .net core, .net core tutorial, .net core guide, asp.net, asp.net core, asp.net core tutorial, asp.net core guide, tutorial, guide, beginner, intermediate, services, service scope, singleton, scoped, transient, singleton service, scoped service, transient service, AddSingleton, AddScoped, AddTransient, singleton vs scoped vs transient

Id: 01C8selSVCY

Length: 10min 11sec (611 seconds)

Published: Thu Aug 29 2019