.Net Foundation On .NET, 9 Apr 2020

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From YouTube: Creating A GraphQL Backend

Description

Continuing with our coverage on GraphQL, Brandon gets into the code of the graphql-dotnet SDK and shows us how to create a GraphQL endpoint.

Learn more: https://codetraveler.io/DotNetGraphQL

[00:51] - GraphQL SDK options for .NET
[02:20] - Adding a GraphQL query
[10:18] - Follow up resources

GraphQL for .NET
https://github.com/graphql-dotnet/graphql-dotnet

Hot Chocolate: A GraphQL Server for .NET
https://hotchocolate.io/

ASP.NET Core docs
https://docs.microsoft.com/aspnet/core/?view=aspnetcore-3.1&WT.mc_id=dotnet-c9-cephilli

#AspNet #Dotnet #GraphQL #WebDev

A

Like the architect in the matrix, you have full control over how you expose data using graph QL. In this episode, we tell you exactly how it's done on the server check it out.

A

Hello and welcome to another episode of on dotnet. My name is jeremy licinus and today we're continuing our graph QL series. If you haven't seen the introduction, go check that out, because today we're taking what we learned and looking at how you stand up a graph, QL endpoint I'm here with Brandon Minich again Brandon welcome back thanks for having me Jeremy. It's almost like you've been here all so tell us a little bit about. We talked about graph QL, but now I want to use it.

A

So I need to stand that up on my back end. What do I do absolutely.

B

So you could start from scratch. Graph QL is a open source framework. It's was created by Facebook, but it's now actually owned by the graph QL foundation similar to the dotnet foundation. But what I recommend is a couple popular SDKs to help us get started and the two most popular ones right now, our graph QL net and hot chocolate. Okay.

A

B

Graph QL dotnet- it definitely is the most popular it has millions of downloads on nougat, and a lot of that is because it was the first graph QL library for us dotnet developers, but there's a rising star, exciting new library called hot chocolate that is quickly gaining traction. So for today's demo, we'll use graph QL net but highly recommend hot chocolate to anybody, who's looking to get started and learn more as well and.

A

My understanding, if I understand graph, kill correctly, whatever SDK I, go with the way that I'm gonna, query and retrieve data is going to be the same. What's changing is the way I'm setting it up on the back end, correct yeah,.

B

Essentially, the the syntax there, implementation may be one uses attributes and the other uses properties. Okay,.

A

Kind of says you.

B

Know choose the one that makes the most sense to you and the one you're most familiar with and most accessible with cool, so yeah, let's jump right into it. Let's, let's write some code, so I have here a graph QL library. This is all done in dotnet core three and because it's all in net I also have code from my mobile app in here, which will show off in our next section where we learn how to consume this API from our mobile app. Okay,.

A

B

For now, let's go ahead and run this API just to show what it's doing right now so right now it's running here on my local host and just like we learned in the last episode we get graphical for free, so I didn't write any code. This just appears when I clicked run and also like we learned in the last episode. We get self-documenting code, so graph graphical automatically combs through my graph QL backend and exposes all the types that are available for us to query.

B

So what we're creating today is a favorite dogs, app I'm, a dog lover, and you know it's always nice to us to be able to have a look at your favorite dog on a mobile, app and so right. Now what we have in our graph, QL back-end, we're able to query for one dog, so I can use what we learned in the last episode and we can type in a specific dog, so we'll type in my dog's name Kirby and then for that dog.

B

There's, a couple different properties that we've exposed and so I can search for the.

A

Title is there a way to ask for all properties, or do you have to spell out exactly what you want every time there.

B

Is not so this is. That was something that tripped me up at first, because I'm used to just querying a REST API I'm used to saying hit this get rest API and give me all the data, and so the first thing I would try. I would do something like this, where I would say, give me everything about Kirby, but no yeah.

A

It yells at me because I.

B

Haven't specified it.

A

Feels that I opted.

B

In model totally.

A

B

Okay, but now that we passed those in well, we can get that information back about Kirby so sure. So this is great, but one of the benefits of graph QL is we don't want to make multiple round trips? We only need to make one round trip with our graph QL endpoint and the way I've designed our import right now. It can't return a list of dogs. So, okay, let's go ahead and jump into the code and add that it sounds like a plan so exploring our our code. Here we have this.

B

We have this images query. So this is what appears when we click on query. So right now we see one field that we can pass in a string for the dog's name and it returns a dog object and looking at the code, we see all the same information, but this is how we can generate that for our endpoint. So we tell it that we want to expose a field and for graac ul we create a graph type for our model.

B

So one cool thing about this is: if I go to this declaration, we're using my dog images model. The dog images model- this is my C sharp object, just properties, getters setters, nothing, fancy just breed birthday coat color, but for a graph QL we can actually specify which fields we want to expose and which ones we don't so things like. Maybe we don't want to share the birthday so if I wanted to I could comment this out and when we rerun our graph QL API and jump back into that documentation Explorer.

B

What we'll see is now. We can no longer query for the birthday, so so we can expose as much or as little data from our model as we want. So it's not like. If something exists in our database or in our code, we have to be able to return. All of that. So.

A

I assume that from a security perspective and we're not gonna dive into that advantage on this show, but you could potentially based on someone's authentication restrict which fields they have access to as well. Right, ok,.

B

Cool yeah, and so so that's how we are exposing those fields, and we were saying we want to also be able to query for all the dogs. So what we'll generate here we'll say: we'll have another field underneath this query, and this will actually be a list list graph type and the type of that will be the dog images graph type, and then we just have to give it a little bit of information. So this is what we'll call it so for the other one. We called it dog because it just returns.

B

One dog so we'll get really creative and call this one dogs and the.

A

Hair on that one and.

B

For the description will say, returns a list of dogs, and you know we're comparing this to the previous one.

B

It's gonna look a little different because the previous one had to have an argument where we passed in the dog's name right, because we were only returning one dog, so we had to tell the user wit or ask the user, which dog for this we're not gonna, require a specific parameter, specific query argument, so we'll just jump down straight to what's called the resolver and there we go, and so the resolver just tells the graph QL endpoint how to get the data. So.

A

When they ask for this, this is how you resolve the request yep, so.

B

Maybe this data is in a database and we could point this to our our sequel database. Maybe we're building a graph, ul API in front of an existing suite of REST API s. We could actually point this to existing REST API s nice. So in this case we'll point it to my my dog images data and we'll just tell it to get all of the dog images and we're getting yelled at no. No. Here, let's go ahead and stop rid of this.

A

Doesn't like the live change? Oh I.

B

See what I did okay I forgot to tell it, because we need to pass in a context. It just so happens, I'm not using the the current context here. This is just basically some dummy data that were returning back. Ok, so now, let's run it and when we run this again we'll see in our documentation, Explorer will see the original dog query, but now here's the new one we just created. So what we're able to do now is create that query where we can request all the dogs, but again just like we said earlier.

B

We can't just say give me all the information about all the dogs. We have to actually specify which information we want, so we can get back the dog's name or the title of the image. The breed and we'll select a couple of these and then.

A

There we go and.

B

Now we have all this list of dogs, so we have waffles and whiskey and Toby all my favourite dogs coming back from our new graph QL API n void. So.

A

It sounds like you have full control over what you're returning it doesn't matter if it's XYZ database, but you have an API that you basically say when I ask for this. This is how you get it and then once you do that the client is off to the races. So it's not like, because I've heard some people say we're passing control to the client and they could just write any query and that's not a good thing, but you've got control over what's being passed. Then exactly.

B

Yeah, just like with any API, will restrict or expose only the data we want so right. We don't have to share any PII like birth dates or passwords, or anything look crazy like that, because nobody needs to see that very good all right. So, if you're wondering where to find this code, it is all available on github and what we've done today, we've put together this webpage.

B

That gives you links of the code a couple of different sample apps and if you want to learn more, there's also more information there, where you can dive into the docs and start learning and building your first graph, hello, API, ed, Boyd, nice.

A

So that's graph QL on the back end in the next episode, we're going to explore how to consume this data from a client so tune in check it out, and thank you for joining us and on dotnet.

A

Hi I'm Jeremy lick nice you've watched another episode of on dotnet. Thank you for joining us, be sure to LIKE and subscribe so that you don't miss a show and if you're interested in more shows check out the link right here. Thanks.