C# 重构：检查派生 class 的类型并分配给相同 class 的变量

Question

我有很多 class 是从一个抽象 class 派生出来的。在一个方法中，我收到一个对象，它是派生的 classes 之一。我需要检查对象的类型并分配给正确的属性。直接的解决方案有效，但看起来可以重构。不过，我不知道如何处理它：

    public MyDerived1 derived1;
    public MyDerived2 derived2;
    // ....
    public MyDerivedX derivedX;

    public void AssignValue(MyBaseClass entity)
    {
        var derivedOne = entity as MyDerived1;
        if (derivedOne != null)
        {
            derived1 = derivedOne;
            return;
        }

        var derivedTwo = entity as MyDerived2;
        if (derivedTwo != null)
        {
            derived2 = derivedTwo;
            return;
        }

        // ....

        var derivedEx = entity as MyDerivedX;
        if (derivedEx != null)
        {
            derivedX = derivedEx;
            return;
        }
    }

Answer 1

您可以像这样创建 AssignValue 的通用版本：

private static bool AssignValue<T>(MyBaseClas entity, out T derived) where T : MyBaseClas
{
    var t = entity as T;
    if (t == null)
    {
        derived = null;
        return false;
    }

    derived = t;
    return true;
}

现在可以这样使用了：

MyDerived1 derived1;
MyDerived2 derived2;

var _ = AssignValue(entity, out derived1)
    || AssignValue(entity, out derived2);

通用函数 returns bool 跳过第一个匹配项的挂起类型检查

Answer 2

也许您正在寻找类似的东西：

    public void AssignValue(MyBaseClass entity)
    {
        var item = this.GetType().GetFields().FirstOrDefault(x => x.FieldType == entity.GetType());
        if (item != null)
        {
            item.SetValue(this, entity);
        }
    }

C# 重构：检查派生 class 的类型并分配给相同 class 的变量

C# Refactoring: check type of the derived class and assign to a variable of the same class

c#

polymorphism

refactoring

derived-class