using System;

public class Program

{

    public static void Main()

    {

    }

}

​

public abstract class Builder<T> where T : new() {

    public Builder() 

    {

        this.ObjectUnderConstruction = new T(); 

    }

    protected T ObjectUnderConstruction { get; private init;}

    public T Build() 

    {

        if (VerifyObjectComplete())

        {

            return ObjectUnderConstruction; 

        }

        else 

        {

            throw new Exception("Builder verification failed or somesuch");

        }

    }

    protected abstract bool VerifyObjectComplete();

}

​

public class TestBuilder : Builder<SomeObject> {

​

    public void SetA(object value) 

    {

        ObjectUnderConstruction.A = value;

    }

    protected override bool VerifyObjectComplete() {

        var verifyA = ObjectUnderConstruction.A != null;

        return verifyA;

    }

}

​

public class SomeObject 

{

    public object A {get; set;}

}