将C#引用类型克隆到派生的引用类型

Question

来自C++背景，我发现在C#中克隆对象有点难以适应。为了澄清我的一些困惑，我正在寻找一种优雅的方法来将基类型的对象克隆到派生类型。

举例说明：

public class Base
{
    public string Member1;
    public int Member2;
    public float Member3;
    public bool Member4;
}

public class Derived : Base
{
    public List<Base> Children;
}

Base base = new Base();

有了这些，我想创建一个“派生”的实例，同时创建一个基本对象的成员副本--最好不要手动分配它们。

注意:也许这会更适合值类型？

Answer 1

由于您不能更改对象的类型，因此您有以下几个选项：

封装Base

• use通过反射或类似的Base 复制来自Base

• copy的值的构造函数

对于后者，MiscUtil有一个有用的工具：

Base b= ...
Derived item = PropertyCopy<Derived>.CopyFrom(b);

对于封装：

public class Derived
{
    readonly Base b;
    public Derived(Base b) {this.b=b;}
    public List<Base> Children;
    public string Member1 {get {return b.Member1;} set {...} }
    public int Member2 {etc}
    public float Member3 {etc}
    public bool Member4 {etc}
}

或作为手动副本：

public class Derived : Base
{
    public Derived(Base b) {
        this.Member1 = b.Member1;
        // etc
    }
    // additional members...
}

或者(注释)获取base来复制它自己：

public class Derived : Base
{
    public Derived(Base b) : base(b) { }
    // additional members...
}
public class Base
{
    // members not shown...
    public Base() {}
    protected Base(Base b) {
       this.Member1 = b.Member1;
        // etc
    }
    // additional members...
}

(其中Base的构造函数初始化来自Base的字段)

Answer 2

/// Clone all fields from an instance of base class TSrc into derived class TDst
public static TDst Clone<TSrc, TDst>(TSrc source, TDst target)
    where TDst : TSrc
{
    var bf = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.FlattenHierarchy;
    foreach (FieldInfo fis in source.GetType().GetFields(bf))
        fis.SetValue(target, fis.GetValue(source));
    return target;
}

/// Create a new instance of a derived class, cloning all fields from type TSrc
public static TDst Clone<TSrc, TDst>(TSrc source)
    where TDst : TSrc, new()
{
    return Clone(source, new TDst());
}