// MyDataGraphType.cs
public class MyDataGraphType : InterfaceType<MyData>
{
    protected override void Configure(IInterfaceTypeDescriptor<MyData> descriptor)
    {
        descriptor.Name("MyData");

        descriptor.Field(f => f.Id).Type<NonNullType<IdType>>();
        descriptor.Field(f => f.Name).Type<StringType>();
    }
}

// FooType.cs
public class FooType : ObjectType<Foo>
{
    protected override void Configure(IObjectTypeDescriptor<Foo> descriptor)
    {
        descriptor.Interface<MyDataGraphType>();

        descriptor.Field(f => f.FooTime).Type<DateTimeType>();
    }
}

// BarType.cs
public class BarType : ObjectType<Bar>
{
    protected override void Configure(IObjectTypeDescriptor<Bar> descriptor)
    {
        descriptor.Interface<MyDataGraphType>();
    }
}

// Query.cs
public class Query
{
    private readonly IMyDataProvider provider;
    public Query(IMyDataProvider provider)
    {
        this.provider = provider ?? throw new ArgumentNullException(nameof(provider));
    }

    public IEnumerable<MyData> ReadAllData(MyDataType dataType)
    {
        return this.provider.ReadAllData(dataType);
    }
}

// QueryType.cs
public class QueryType : ObjectType<Query>
{
    protected override void Configure(IObjectTypeDescriptor<Query> descriptor)
    {
    descriptor.Field(f => f.ReadAllData(default))
        .Type<ListType<MyData>>()
        .Argument("dataType", a => a.DefaultValue(MyDataType.None));
    }
}

// Startup.cs
    services.AddTransient<IMyDataProvider, DummyDataProvider>();
    services.AddGraphQL(sp => SchemaBuilder.New()
        .AddServices(sp)
        .AddQueryType<QueryType>()
        .AddType<FooType>()
        .Create());