Introduction to GraphQL in .Net Core

GraphQL, a powerful API query language, emerges as a dynamic alternative to REST due to its flexibility in handling complex data structures. While REST offers a structured resource-oriented approach, GraphQL addresses the limitations encountered when client requirements evolve rapidly. This blog delves into the fundamentals of GraphQL, its advantages over REST, and provides a sample implementation using ASP.NET.

Configuration

Incorporating GraphQL into an ASP.NET application involves configuring the pipeline to handle Get and Post requests. Below is a snippet from the program.cs file illustrating the setup:

var builder = WebApplication.CreateBuilder(args);

// Add graphql services to the DI container
builder.Services.AddGraphQL();

var app = builder.Build();

// Configure the HTTP request pipeline
app.UseGraphQL();
app.Run();

Graph Controller

Instead of utilizing a standard web API controller, GraphQL introduces the concept of a graph controller. The example below showcases a HeroController with a sample query for retrieving data based on query input:

public class HeroController : GraphController
{
    [QueryRoot]
    public Human Hero(string episode)
    {
        if(episode == "Empire")
        {
            return new Human()
            {
                Id = 1000,
                Name = "Han Solo",
                HomePlanet = "Corellia",
            }
        }
        else
        {
            return new Human()
            {
                Id = 1001,
                Name = "Luke SkyWalker",
                HomePlanet = "Tatooine",
            }
        }
    }
}

Sample Query

query {
    hero(episode: "Empire") {
        name
        homePlanet
    }
}

Json Result

{
    "data" : {
        "hero": {
            "name" : "Han Solo",
            "homePlanet" : "Corellia"
        }
    }
}

Contrary to common misconceptions, GraphQL is not a database methodology but a query language structured for APIs. This introductory guide provides insight into passing queries and obtaining JSON results. Stay tuned for our upcoming blog, where we explore creating CRUD operations using GraphQL with GraphQL Types and Collections. We hope this serves as a valuable introduction to the world of GraphQL.