// In startup.cs

var schema = FederatedSchema.For(
    schemaString
    _ =>
    {
        _.Types.Include<Query>();
        _.Types.Include<Mutation();
        ...
    };
services.AddTransient<Query>().AddTransient<Mutation>().AddSingleton(schema);

// In Query.cs
public class Query
{
    private readonly IDataProvider provider;
    public Query(IDataProvider provider)
    {
        this.provider = provider;
    }
}

// Exception received:
No parameterless constructor defined for type 'Query'