corstian / Boerman.GraphQL.Contrib

Library containing some helper methods for GraphQL apis. Includes data-loaders and (cursor based) pagination helper methods.

GraphQL Helper Methods

This library contains a bunch of methods to make my life as developer easier. Some common tasks have been abstracted away in reusable and composable sections.

Functionality

The main reason to use this library are the following methods:

• Slice() - An extension method to the Query object (SqlKata) which applies cursor based pagination to the provided query.
• ToConnection() - An extension method to the Query object which applies pagination (using the Slice method) and returns a Connection object.
• EntityLoader() - An extension method on the IDataLoaderContextAccessor to retrieve a single value via the data-loader based on a LINQ predicate. The loader will combine all similiar requests.
• EntityCollectionLoader() - An extension method on the IDataLoaderContextAccessor to retrieve multiple values based on a LINQ predicate. The loader will combine all similiar requests.
• A more natural way to add authorization to queries. A detailed blog post explaining this functionality is available here.

Usage

Slice

new Query("Companies")
    .Where("City", "Amsterdam")
    .Slice(
        after: "cursor",
        first: 25);

ToConnection

Connection<Company>()
    .Name("companies")
    .ResolveAsync(async context => {
       return await new Query("Companies")
            .Where("City", "Amsterdam")
            .ToConnection<Company, object>(context);
    });

EntityLoader

Field<AircraftType, Aircraft>()
    .Name("aircraft")
    .ResolveAsync(async context =>
    {
        return await dataLoader.EntityLoader(
            dbProvider.Get().Aircraft,
            aircraft => aircraft.Id,
            context.Source.AirfieldId);
    });

EntityCollectionLoader

List<Flight> flights = await dataLoader.EntityCollectionLoader(
    dbProvider.Get().Flights,
    flight => flight.AircraftId,
    context.Source.Id)

Installation

You can copy some specific code over from this repository or you can install the whole package via NuGet.

Install-Package Boerman.GraphQL.Contrib

or

dotnet add package Boerman.GraphQL.Contrib

Dependencies

This library has quite a few dependencies. This comes from my own workflow where I start using Entity Framework, and use SqlKata for some specialized logic. Because Entity Framework acts as my base I also reuse the data models with SqlKata.

Further content

All of this functionality has been documented over the course of several blog posts:

• Implementing pagination with GraphQL.NET and Relay
• Cursor based pagination with SQL Server using C# (and SQL)
• Generic data loaders for Entity Framework in GraphQL