abstract class ClassePaiBuilder<T> where T : ClassePaiBuilder<T> {
    public T SetAtributo(string atributo) {
        // codigo
        return (T)(object)this;
    }
 
    public object Build() => new object();
}
 
class ClasseFilhaBuilder : ClassePaiBuilder<ClasseFilhaBuilder> {
    public ClasseFilhaBuilder SetOutroAtributo(string outroAtributo) {
        // codigo
        return this;
    }
}
 
public class Program {
    public void Main() =>
        new ClasseFilhaBuilder()
            .SetAtributo("atributo da classe pai")
            .SetOutroAtributo("atributo da classe filha")
            .Build();
}
 
//https://pt.stackoverflow.com/q/92654/101

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