public class MyDbContext : DbContext {
  protected override void OnModelCreating(ModelBuilder builder) {
    // Set up your relations
  }

  public DbSet<Property> Properties { get; set; }
  public DbSet<PropertyType> PropertyTypes { get; set; }
  public DbSet<Location> Locations { get; set; }
}

public class Property {
  public uint Id { get; set; }
  public string Name { get; set; }
  public PropertyType Type { get; set; }
  public Location Location { get; set; }
}

public class PropertyType {
  public uint Id { get; set; }
  public string Name { get; set; }
  public decimal Premium { get; set; }
}

public class Location {
  public uint Id { get; set; }
  public string Name { get; set; }
}

public class Startup {
  public void ConfigureServices(IServiceCollection services)
  {
      services.AddDbContext<MyDbContext>(opt => opt.UseInMemoryDatabase());
      // add schema provider so we don't need to create it everytime
      // Also for this demo we expose all fields on MyDbContext. See below for details on building custom fields etc.
      services.AddSingleton(SchemaBuilder.FromObject<MyDbContext>());
  }
}

[Route("api/[controller]")]
public class QueryController : Controller
{
    private readonly MyDbContext _dbContext;
    private readonly MappedSchemaProvider<MyDbContext> _schemaProvider;

    public QueryController(MyDbContext dbContext, MappedSchemaProvider<MyDbContext> schemaProvider)
    {
        this._dbContext = dbContext;
        this._schemaProvider = schemaProvider;
    }

    [HttpPost]
    public object Post([FromBody]string query)
    {
        try
        {
            return _dbContext.QueryObject(query, _schemaProvider);
        }
        catch (Exception)
        {
            return HttpStatusCode.InternalServerError;
        }
    }
}

// Build from object
var schema = SchemaBuilder.FromObject<MyDbContext>();

// custom fields on existing type
schema.Type<Person>().AddField("totalChildren", p => p.Children.Count(), "Number of children");

// custom type
schema.AddType<TBaseEntity>("name", "description");
// e.g. add a new type based on Person filtered by an expression
var type = schema.AddType<Person>("peopleOnMars", "All people on mars", person => person.Location.Name == "Mars");
type.AddPublicProperties(); // add the C# properties
// or select the fields
type.AddField(p => p.Id, "The unique identifier");
// Add fields with _required_ arguments - include `using static EntityGraphQL.Schema.ArgumentHelper;`
schemaProvider.AddField("user", new {id = Required<int>()}, (ctx, param) => ctx.Users.FirstOrDefault(u => u.Id == param.id), "description");

// Here the type schema of the parameters are defined with the anonymous type allowing you to write the selection query with compile time safety
// You can also use default()
var paramTypes = new {id = Required<Guid>()};

// If you use a value, the argument will not be required and the value used as a default
var paramTypes = new {unit = "meter"};

public class PropertyMutations
{
  [GraphQLMutation]
  public Property AddProperty(MyDbContext db, PropertyArgs args)
  {
    // do your magic here. e.g. with EF
    var property = new Property { Name = args.Name, ... };
    db.Properties.Add(property);
    db.SaveChanges();
    return property;
  }
}

public class PropertyArgs
{
  public string Name { get; set; }
  public Decimal Cost { get; set; }
}

schemaProvider.AddMutationFrom(new PropertyMutations());

// we create a schema provider to compile the statement against our Property type
var schemaProvider = SchemaBuilder.FromObject<Property>();
var compiledResult = EqlCompiler.Compile(myConfigurationEqlStatement, schemaProvider);
// you get your list of Properties from you DB
var thingsToShow = myProperties.Where(compiledResult.Expression);

// You'd take this from some configuration
var eql = "if location.name = 'Mars' then (cost + 5) * type.premium else (cost * type.premium) / 3"
var compiledResult = EqlCompiler.Compile(eql, schemaProvider);
var theRealPrice = compiledResult.Execute<decimal>(myPropertyInstance);