Adding a Service to an ASP.NET Core Website | ASP.NET Core 101 [4 of 13]


>>Hey friends. We’re
creating an ASP.NET website. We’re doing it the 101 style, real slow, very deliberately. In the last video, we’re
starting to bring in data. We haven’t actually displayed it yet because we want to do this right. We’ve made a little JSON file and that’s our database
for this purpose. Then, what we’re going to do is
we’re going to add a service, and ASP.NET has this
concept of services. We’re going to try to do that in
a very deliberate way as well. So you’re clear on how we’re doing.>>So why even make a
service to begin with? Why can’t I just take
this code wherever I wan?>>That’s a great question. So we tried to do this
in such a way that it is going to be
maintainable for the future.>>Makes sense.>>We could theoretically just
make like one or two lines of code that open this thing up and
just split it out to the screen. But other people might
want to use this. We might want to be able to
reuse it in different places. So we’re going to try
to be a little bit more deliberate and use some of the cool features that are built into ASP.NET to make that possible.>>So in this context,
service is like if you’re at a restaurant and the waiter asks you what you want and you can request.>>That’s a really great point. Because a service in the
context of the computer is I need something and I
need you to get it done. I don’t even know how you
doing it, the waiter.>>I don’t want to do the work.>>Don’t talk to me, just get
me that thing that I need. So what we could do of
course is make it so our webpage loads that file up
off disk and then just goes blip. But let’s separate some concerns. Let’s have what’s called the
single responsibility principle. So where do we want to do? I remember that in the
last video you had me make a models folder and
inside that is product.>>So why don’t we do something
similar where we create a services folder in that same spot, so in the root of the project?>>So we’re going to
go and say Add and I’m going to say New Folder, and you want to call it services. We’ll put all of our
future services in there. Then right now, we’re storing
our data in this JSON file. So this is a JSON file service thing.>>Yeah. We’ve got to have a spot to actually extract that
data to begin with. So let’s create a file and call
it the JsonFileProductsService.>>JsonFileProductsService.
That makes sense. It’s very descriptive and it
told me exactly what it does. So this JsonFileProductsService is going to be a little complicated. So for the purposes of this rather than you watch me
type the whole thing, I am going to Copy Paste this from a GitHub jist to be able to
find that in the descriptions or in the GitHub Repository for Contoso crafts so that if you’re
following along, you can do that.>I was looking up at
guest earlier and they were using product
service, not products.>>So we’ll want to watch for that. So I’ve said products
and you might have a similar thing if you’re following along when you spell something
slightly differently. Good call, we’ll watch for that. So I’m going to go and change that, Paste over the top. So I’m taking this and
I’m Pasting over here, JsonFileProductService,
and that’s fine. I could even rename the file
to make it match the problem.>>Cool. So we have here a lot of code and suddenly
things became very scary. Why don’t we do this? When
you’re in Visual Studio, it is a text editor. It’s like Notepad but
it’s a smart text editor.>>So that means it
can probably identify what the functions are
that we just made.>>It can. What’s really great point if we go over here look at this, we can actually zoom in
and we try zooming in, and in the solution editor, we get like our properties the ones that are
private a little lock, the message that’s cool, but also the Smart Text Editor
will allow me to collapse.>>What do you know?>>It’s called a
collapsing text editor.>>So much nicer.>>It is. It’s also less, for lack of a better
word, threatening because it’s like
yeah , let’s get it.>>Or if you just want to get
all the clutter out of the way.>>Absolutely, out of
sight, out of mind.>>Exactly.>>So let’s see what’s going on here. We have a thing called
JsonFileProductService. This is our constructor. Well, web applications are
hosted, they live in a host. They’re actually Console apps. I’ve been making Console
apps with Kendra. Do you know that an ASP.NET
app is a Console app as well?>>Oh, a small world.>>So if you go to program.cs, there is a main except it’s not a main that
says console.writeline, it’s a main that makes the host.>>That’s cool. Is telling
something else what to do as well.>>Exactly. So I want to know about that environment.
What’s going on here? We have an IWebHostEnvironment
and then we’re keeping it. We’re getting it passed
in and we’re keeping it.>>So I think how that is
going to work is that it will allow us to
retrieve that JSON file. So we can let this WebHostEnvironment know the path where
this file comes from.>>So that’s a great point.
In this folder right here, we have wwwroot, data, products. I don’t want to hard code that C:\.>>We’re going to mess it up anyway.>>You know I’ll mess it up.
So the WebHostEnvironment will know where things are located. So what I’m going to do
is in my constructor, I’m going to have an
argument that asks ASP.NET, “Hey, give me one of these.” What’s cool about this is
I never have to make one. There’s nowhere in this
code where I knew it up. It’s just handed to me. Then, where is the file located? Look at this, this is interesting. We made a property
called JsonFileName. Again, either one of us could
have just hard coded C:|. But what we did is we said, “Hey, WebHostEnvironment,
where is the web root?” Your disk and my disk and
their disk is different. They might be on the D drive, they may be in SQL
and Leslie who knows.>>If you move it somewhere else?>>You don’t want them to
break. So this is cool. We’re going to use an another
library called System.IO.Path. We’re going to combine three parts. So the first one is wwwroot, the next one is data, and you can combine as many passes
as you want and they’re taking care of the slashes and the
backslashes and this and that.>>The perk about putting
that Products.JsonFile in the wwwroot folder that we have is because that web root path will just automatically go to level.>>It will be absolutely reliable. It gets the path to the directory
that has webserver application. Now, we could have put that in a
number of different folders and WebHostEnvironment also has
other ones like content route. So there’s multiple places
we could have put it. So maybe if you’re an advanced
person and you’re watching, you may have an opinion about that. Just know that there’s
lots of different places. So the one we’re using
is web root path. So WebHostEnvironment, we’ll talk a little bit
about that in a minute, is a service that is being given to our service so it’s
a chain of services.>>Shared services.>>Shared services.>>Sharing is caring.>>Indeed. Here’s the part
that gets a little intense. This took me a second to
get my head around this.>>So what’s happening here? We are retrieving the products. How are we doing that?>>So I innumerable is not listed
because I’ve been doing this.>>Yeah. So in this case, now that we’ve retrieved
that JSON file, we have to convert that text into the actual product that we
defined back in the last video. So to do that, we talked
before about serializing. In this case, we’re de-serializing. So we’re taking that JSON
text and converting it into the object that we created.>>So let’s look at that really
briefly, remind ourselves. Here’s what the JSON looks like. Here’s what the product is shaped like and we’re going to have
a list of these things. What we’re going to
do is we are going to open up that text file with
that filename we made before.>>Yeah.>>As you said, we’re going to de-serialize
and this is interesting, we’re making an array of products, not one product but products. That means an array or
a list of products. We’re going to read that
JSON file to the end. You can read just one
line, we want it all.>>Our product circle here.>>Here, we can pass in some optional options and these are not required, they are optional. We’re saying don’t really care about uppercase lowercase,
just make it work.>>Yeah.>>Because I can’t
deal with the stress.>>I agree.>>Then, this is interesting and
IEnumerable, I was using lists.>>Me too I typically use lists.>>List of this, list of that. IEnumerable is the great
great grandparent of lists. It’s stuff that you can four each over, that’s how
I think about it. So if take a look at the video
that we did with Kendra on C#, we talked about ‘for’
loops and ‘for eaches’, things that you can ‘for’ each over are things that you can enumerate. Therefore, they are
enumerable things.>>That’s nice because
I’m not limited to just having to use lists.>>Yeah.>>I can use whatever
IEnumerable that want.>>Exactly. In this case,
I’m using an array, I could use a list, I could use a collection, it’s totally up to me. So let’s just recap. What we’re doing here is we
have a service whose got one job and to give us a list of products or an
enumerable of products. But how do we tell the
system about that? How do we publicize it? We have a waiter now, tell everyone in the restaurant
there’s a waiter.>>Yep. So in that case, we have to get the file and then
open it up and then convert that text into the
product object that we created.>>We need to make sure that ASP.NET knows that this is an
available service. So I’m going to go over to startup. In startup, this is a
special ASP.NET page. This is especially as you get
on that bit of code rather.>>So in the past,
this is usually one of those files that I just
ignore or glance over. I think it’s not important
because there’s a bunch of complicated things on there already.>>To be honest, it does look like a bunch of boilerplate code, it is. With the program part
of the program CS, this is usually like
console.writeline. For us it’s CreateHost. Here, we say “Hey, use Startup.” That’s our startup class. It can be called Fred or Foo or
whatever, we call it Startup. What it is is it’s a special
file that has a couple of methods that we want to
care about and the methods are Configure and ConfigureServices. This is really interesting
because we never actually again make a start-p class. It gets made for us and we don’t
make a JsonFileProductService, it gets made for us. So remember how you said
that we were going to make a JsonFileProduct as a service?>>So it makes sense to stick
it in configure surfaces.>>Exactly right. So what we
want to do is we want to go into ConfigureServices and we’re going to tell it about this new service. You can see that razor pages that we’re going to talk
about in a little bit. It’s a kind of service. So I can
say services. Now look at this.>>I’m liking the stars
here in telecode action.>>Yeah. So that’s a great point. In telecode, is a really
smart way to give you auto-complete and the stars are
the ones that are most likely.>>Yeah.>>So it’s actually got it right.
The one I want is transient. There’s two major ones, singleton which is, just make it so there’s
only one of these surfaces. Then transient, a transient is
a thing that comes and goes. So you’re going to get a new one of these every
time you ask for it.>>Yeah. So in this case, the service that we
want to connect to you is our JsonFileProductServices.>>JsonFileProductService. Notice that it’s not autocompleting.>>We made up. I
think part of that is because we named our
file something else.>>In fact, I renamed it and the issue is that it’s in
a different namespace.>>Yep, that’s it.>>So I’m going to hit
”Using” and I’m going to hit “Enter” and you’ll see that it actually just added
that line right there. But you make a really good point. It’s worth pointing out
that if you had named it differently, it wouldn’t allow it up.>>Yeah.>>Like if I did this,
see it’s not blue. So you definitely want to know about your spellings and make sure that
everything is exactly correct. So what we’ve done is we’ve
told the system about this. So now, the service
that we just made Is a member of this collection of services and it’s a
Transient service, it comes and goes as it likes.>>No one’s going to know
about your restaurant. Must you stick it and out?>>I’m actually publish it. Exactly and this service
collection it’s a great point, it’s an advertisement
for all of ASP.NET that this is a thing and then you can go and do your stuff with that thing. There’s lots of services
and we’ll add a bunch. We’ve got routing and endpoints
and all kinds of stuff like that. So at this point, it’ll
probably compile, it will probably run.>>Across.>>So we have such low
expectations ourselves. It’ll probably run
and it probably still won’t show anything
because I’m silly. Let’s find out. They’ll
have no data. Okay.>>Awesome.>>So you might be saying, “Hey, Scott Leslie you have two videos
in and you haven’t it show in.”>>It’s crafts.>>” What’s going on?
Where are the crafts? We want the crafts.” The reason is that we
want to do this right. Here is some data. This
could come from a file, it could come from a database, it could come from lots of places. We want to have a service that’s smart about how to
retrieve that data, we want you to understand
how that data comes out. But now that we’ve published it, we’ve told our ASP.NET
application that this exists, I bet we’re going to be able
to get data pretty done soon.>>I’m so excited.>>Stick with us for the next video.

One Reply to “Adding a Service to an ASP.NET Core Website | ASP.NET Core 101 [4 of 13]”

  1. Wonderful videos for starting development in .net. Can't thank you enough.
    One suggestion about this video. You should have created folder per entity/ feature instead of folder for Models, Services etc.

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