GraphQL.EntityFrameworkCore.Helpers 1.0.1

GraphQL Helpers for EF Core

Adds methods to resolve schema fields directly from a DbContext. See sample project for a full setup reference.

Getting Started

You can install the lastest version via NuGet.

> dotnet add package GraphQL.EntityFrameworkCore.Helpers

And edit Startup.cs to register dependencies by calling method below in ConfigureServices(IServiceCollection services). Passing DbContext as type parameter is optional, if it isn't passed here it would need to be passed when defining the schema fields.

public void ConfigureServices(IServiceCollection services)
{
    services
        .AddGraphQLEntityFrameworkCoreHelpers<AppDbContext>();
}

Defining the Schema

To resolve a root query from the DbContext using the helper methods you first need to call the From method with the DbSet to be included and then call either ResolveCollectionAsync for a list graph or ResolvePropertyAsync for a non list graph.

Field<ListGraphType<HumanGraphType>>()
    .Name("Humans")
    .From(dbContext.Humans)
    .ResolveCollectionAsync();

You can also add connections in a similar way. With the connections the client has the option to define what property/properties should be used to order the connection. Read more about connections here.

Connection<DroidGraphType>()
    .Name("Droids")
    .From(dbContext.Droids)
    .ResolveAsync();

The helper methods can also be used to resolve data loaded properties. Read more about data loaded fields here.

public class HumanGraphType : ObjectGraphType<Human>
{
    public HumanGraphType()
    {
        Field<PlanetGraphType, Planet>()
            .Name("HomePlanet")
            .Include(x => x.HomePlanet)
            .ResolveAsync();
    }
}

Applying business logic when resolving fields

With all builders you can apply your own business logic to for instance support authorization scenarios by calling the method Where.

Field<HumanGraphType, Human>()
    .Name("BestFriend")
    .Argument<NonNullGraphType<IdGraphType>>("HumanId")
    .Include(x => x.Friends)
    .Where(context =>
    {
        var humanId = context.GetArgument<int>("HumanId");
        return x => x.BestFriendId == humanId;
    })
    .ResolveAsync();

Validating the context

Similarly you can validate the arguments passed to a context using either Validate or ValidateAsync.

Field<PlanetGraphType, Planet>()
    .Name("HomePlanet")
    .Include(dbContext, x => x.HomePlanet)
    .ValidateAsync(async context =>
    {
        var result = new ValidationResult();
        var hasAccess = await UserValidator.HasAccessTo(context.GetArgument<int>("id"));

        if (hasAccess == false)
        {
            result.failures.Add(new ValidationFailure("id", "No access"));
        }

        return result;
    }))
    .Apply((query, context) => query.Where(x => x.Id == context.GetArgument<int>("id")))
    .ResolveAsync();

Filters

All collection fields can be filtered by either applying a string to all filterable properties using Or or applying specific rules for specific properties. Read more about filters here.

Avoiding Over-Fetching

All helper methods tries to limit the amount data fetched from data store by looking at what was requested, read more about this here.