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Learn how you can use GraphQL in .NET Core and C#

Chris Noring on August 02, 2019

GraphQL is this technology created by Facebook that enables the frontend to negotiate with the backend for what data it wants. It also enables the...

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Peter Dolkens • Aug 12 '19 • Edited

Has anyone actually bothered figuring out how to make GraphQL efficient in .Net yet?

Using something like LINQ and EF, I can optimize my database queries to only request the data I need for a REST query - and I can do so with minimal bootstrapping.

In most situations, I can just re-use a repo or unit of work with a custom DataModel, and only have to write a simple LINQ query to get results.

I'm yet to see a GraphQL implementation which isn't simply massive amounts of extra code in the backend, with no clear approach for optimizing the database queries, and a tendency to offer mutators that require access to the majority of your database.

I wish GraphQL evangelists would stop focusing on how pretty the UI code is, when all they're doing is moving the mess somewhere else, and breaking lots of existing optimizations in doing so.

Example - check out the REST API below that looks just a firstname/lastname/id/booking-count up from a potentially heavy profile table. I'd genuinely love to see an efficient and scalable way to tackle this for GraphQL as our mobile guys are chomping at the bit for GraphQL, but I'm yet to see an approach that doesn't involve massive overhead for our team.

public class LiteProfileModel {
    public Int32 ID { get; set; }
    public String FirstName { get; set; }
    public String LastName { get; set; }
    public Int32 Bookings { get; set; }
}

public class ProfileService {
    private readonly IUnitOfWork _unitOfWork;

    public ProfileService(IUnitOfWork unitOfWork) => this._unitOfWork = unitOfWork;

    public LiteProfileModel[] GetLiteProfileByEmailAddress(String emailAddress)
    {
        return this._unitOfWork.Profiles
            .Get(filter: profile => profile
            .Where(p => p.emailAddress == emailAddress)
            .Select(p => new LiteProfileModel 
            {
                ID = p.ID,
                FirstName = p.FirstName,
                LastName = p.LastName, 
                Bookings = p.Booking.Count()
            })
            .ToArray();
    }
}



public class LiteProfileApiModel {
    public Int32 ID { get; set; }
    public String FirstName { get; set; }
    public String LastName { get; set; }
    public Int32 Bookings { get; set; }
}

public class ProfileController : ApiController
{
    private readonly IProfileService _profileService;
    private readonly IMapper _mapper;

    public ProfileController(IProfileService profileService)
    {
        var config = new MapperConfiguration(cfg => {
            cfg.CreateMap<LiteProfileApiModel, LiteProfileModel>();
        });

        this._profileService = profileService;
        this._mapper = config.CreateMapper();
    }

    public LiteProfileApiModel[] Lookup(String emailAddress)
    {
        var results = this._profileService.GetLiteProfileByEmailAddress(emailAddress);
        return this._mapper.Map<LiteProfileApiModel>(results);
    }
}

Chris Noring • Aug 12 '19

You have a lot of great points Peter. Let me come back to you with an article describing a nested implementation and some good practices and how to tackle the N+1 problem.. I'll say this though, you are right, you are moving the problem to somewhere else, from frontend to backend.. As always it's meant to be used in specific cases not to replace REST but coexist. I'll come back with an article in 2-3 weeks, currently on holiday

Peter Dolkens • Aug 12 '19 • Edited

As always it's meant to be used in specific cases not to replace REST but coexist

Yup - my approach so far has been to provide REST APIs in the .Net portion of our stack, and allow the Swift guys to implement a GraphQL aggregator if they care enough for one.

Unfortunately, our database isn't normalized nearly as much as it should be, so pulling back entire tables hurts massively, and I'm yet to find any nice Linq2Sql or similar approaches that eliminate that as an overhead when implementing GraphQL on the .Net side.

I think this is primarily due to maturity of the toolchains, as from what I've seen, the Swift guys are going through the same overhead - it's just .Net has spent decades perfecting the REST approach to the point where I can mock one up in a comment section from memory. Our Swift guys seem to go through the same overhead regardless of REST or GraphQL at the moment however.

Kyrylo Yakymenko • Nov 17 '19

Thanks for the post! Have you had time to write a follow-up article on this? I am particularly curious about tackling the N+1 problem myself.
Also, if you have any tips about implementing a Relay-compatible GraphQL server in .NET (C# or F#), that would be really helpful!

Paul VanRoosendaal • Jan 3 '20

Are you looking for a GraphQL to LINQ translation? Aren't there some libs for that?

Ronaldo Peres • Dec 10 '19

Hi,

Is there an effective way of using GraphQl with MongoDb?

Chris Noring • Dec 10 '19

is this for .NET or? you could be using this github.com/remorses/mongoke to expose your database as a GraphQL API or have a look here if you just want a tutorial on how to use it dev.to/alvarojsnish/graphql-mongod... . Let me know what you had in mind ? :)

Ronaldo Peres • Dec 10 '19

Well,

I am thinking to use GraphQl with Dotnet Core, for example: if I have a collection in mongo of games - how to use GraphQl to retrieve data without doing a GetAll() in the collection?

Is there a way to setup the Mongodb repository in Dotnet core with GraphQl?

Chris Noring • Dec 10 '19

Generally, you use a query that takes a parameter on the GraphQL side

// schema
{
  Query {
    GetCommentById(id: ID): Comment
  } 
}

// asking the query
query <name it something> {
  GetCommentById(id: 1)
}

As for dealing with .NET Core and MongoDB you have a tutorial here docs.microsoft.com/en-us/aspnet/co... . I suppose I could be writing a tutorial on GraphQL, .NET Core and MongoDB if you are interested?

Also have a look here dev.to/dotnet/how-you-can-build-a-... This shows how our request is passed from API to DB layer

jghx • Feb 21 '20

I tried do to a combination of GraphQL, .NET Core and MongoDB but can seem te get the MongoDb working to you still need to use a DBContext and DBsets or can you just use IMongoCollection's like in the Microsoft tutorial?

Noam Wertheim • Mar 30 '20

Hi thank you for the links.
I would be very much interested in reading a tutorial on how to implement a GraphQl server with .NET Core and MongoDb.
So far only managed to implement it when all data sat in memory, which is of course not an acceptable solution.

Chris Noring • Mar 31 '20

I'm looking into a GraphQL solution currently called Hot Chocolate. It has the concept of loaders. Yes some data need to sit in memory, but not all. Maybe that can offer a path forward? hotchocolate.io/docs/introduction....

Daniel Lo Nigro • Aug 3 '19

Great post!

Just a small note:

It's a very cool piece of technology and it's not just for JavaScript

Note that the original use case for GraphQL wasn't JavaScript, it was Facebook's native mobile apps :)
It evolved to JavaScript later on, once Relay (and then Apollo) were released.

Chris Noring • Aug 3 '19

Didn't know that, thanks Daniel :)

Nishant Koli • Feb 20 '20

Thank you for this amazing tutorial. I am a frontend dev trying to understand and implement a backend with graphql.

Forgive me for being naive, but I wanted to know how this is different from a REST api as we are still writing predefined queries to fetch from the db.

Mark Pieszak • Aug 2 '19 • Edited

Great post as always 🙌👏!
I've actually never had a chance to see/try GraphQL with DotNet yet.

Most DotNet shops typically only do REST APIs unfortunately! :(

How is the intellisense with the Queries themselves?

Chris Noring • Aug 2 '19

Well there is the visual GraphiQL NuGet package that will do that :)

Dan Harries • Aug 7 '19

Hi Chris,

I barely comment on dev posts but really like your writing style, very clear and concise.

Keep up the good work 🙂

Chris Noring • Aug 7 '19

Hi Dan, really appreciate your comment, thank you :)

Lee Oades • Aug 8 '19

Great article. Really enjoyed the writing style and pace. Quick typo : "Exuting our query the API"

Mrinal Patra • Aug 8 '19

Great post to get started on GraphQL! I couldn't figure out how to use the DataLoader to batch requests.

Is it possible to have a small example of DataLoader in your follow up post?

Chris Noring • Aug 8 '19

Hi thanks Mrinal. Let me see what I can do :)

Andrés Pérez • Aug 2 '19

Lovely post, would be amazing to see a follow-up GraphQL + ASP.NET Core article :)

Chris Noring • Aug 2 '19

should be coming out next week :)

Carl Sixsmith • Aug 3 '19

Great post, look forward to seeing the next one.

This could be exceeding useful for what I’m currently working on

Pawan Chaurasia • Aug 6 '19

Can you do a graphQL and elastic search tutorial. to access nested data in elasticsearch

Bruno Dantas • Oct 4 '22

LesPinter • Feb 6 '20

I was with you up until "Schema update". Where does this code go?

Chris Noring • Feb 6 '20

we are still in Program.cs at this point. Thanks for the comment. I'll make sure to write out the file name and write out all the code, not just snippets. Have a look at this repo for a more real looking approach github.com/softchris/graphql-ef-demo

Ronaldo Peres • Nov 22 '19

Very good,

I would like to see a tutorial to use graphql with dotnet core 3 webapi.

Regards

Chris Noring • Nov 22 '19

hi Ronaldo. You are in luck :) dev.to/dotnet/how-you-can-build-a-...