The query type in GraphQL represents a read-only view of all of our entities and ways to retrieve them. A query type is required for every GraphQL server.

type Query {
  books: [Book!]!
  author(id: Int!): Author
}

Clients can query one or more fields through the query type.

query {
  books {
    title
    author
  }
  author(id: 1) {
    name
  }
}

Queries are expected to be side-effect free and are therefore parallelized by the execution engine.

Usage

A query type can be defined like the following.

public class Query
{
    public Book GetBook()
    {
        return new Book { Title  = "C# in depth", Author = "Jon Skeet" };
    }
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services
            .AddGraphQLServer()
            .AddQueryType<Query>();
    }
}

A query type is just a regular object type, so we can do everything we could do with an object type with the query type (this applies to all root types).