c# - 构造函数未被调用

Question

public class Unit
{
    public int UnitId { get; set; }
    public Engine EngineStuff { get; set; }

}
public class Engine
{
    public int PS { get; set; }
    public int MaxSpeed { get; set; }
}

var unit = new Unit();
unit.UnitId = 3; //OK because Unit-constructor was called
unit.EngineStuff.PS = 200; //error, because EngineStuff-constructor obviously wasn't called.

如何调用这个“内部”构造函数？我以为它会自动初始化它？

我怎样才能简单地为“EngineStuff.PS”属性赋值？

Answer 1

您必须显式实例化对象的属性:

public class Unit
{
    public Unit()
    {
        EngineStuff = new Engine();
    }
}

---

或者如果您想手动控制何时实例化:

var unit = new Unit();
unit.UnitId = 3; 
unit.EngineStuff = new Engine();
unit.EngineStuff.PS = 200;

或更简单:

var unit = new Unit { UnitId = 3 };
unit.EngineStuff = new Engine { PS = 200 };