GraphQL.EntityFrameworkCore.Helpers 0.5.0

GraphQL Helpers for EF Core

Adds methods to resolve schema fields directly from a DbContext.

Getting Started

dotnet add package GraphQL.EntityFrameworkCore.Helpers

And register GraphTypes to DI:

services
    .AddGraphQLEntityFrameworkCoreHelpers();

Defining the Schema

To resolve a root query from a DbContext using the helper methods you first need to define from what DbContext and what DbSet and then call either the ResolveCollectionAsync method or the ResolvePropertyAsync method.

Field<ListGraphType<HumanGraphType>>()
    .Name("Humans")
    .From(dbContext, x => x.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 with. Read more about connections here.

Connection<DroidGraphType>()
    .Name("Droids")
    .From(dbContext, x => x.Droids)
    .ResolveAsync(typeof(ConnectionInput));

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

Field<PlanetGraphType, Planet>()
    .Name("HomePlanet")
    .Include(dataLoaderAccessor, dbContext, x => x.HomePlanet)
    .ResolveAsync();

Applying business logic when resolving fields

With all builders you can apply your own business logic to for instance support multi-tenant solutions using the method Apply.

Field<PlanetGraphType, Planet>()
    .Name("HomePlanet")
    .Include(dataLoaderAccessor, dbContext, x => x.HomePlanet)
    .Apply((query, context) =>
    {
        var id = context.GetArgument<int>("id");
        return query.Where(x => x.Id == id);
    })
    .ResolveAsync();

Validating the context

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

Field<PlanetGraphType, Planet>()
    .Name("HomePlanet")
    .Include(dataLoaderAccessor, 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.