在派生类中定义重载时,C#后期绑定方法重载不起作用

我需要使用c#late binding features在运行时根据对象的类型调用方法重载.当所有重载都在调用发生的同一个类中定义时,它工作正常.但是当在派生类中定义重载时,它不会在运行时绑定.

class BaseT
{}

class DerivedA : BaseT
{}

class DerivedB : BaseT
{}

class Generator
{
    public void Generate(IEnumerable<BaseT> objects)
    {
        string str = "";
        foreach (dynamic item in objects)
        {
            str = str + this.Generate(item); //throws an exception on second item
        }
    }

    protected virtual string Generate(DerivedA a)
    {
        return " A ";
    }        
}

class DerivedGenertor : Generator
{
    protected virtual string Generate(DerivedB b)
    {
        return " B ";
    }
}



class Program
{
    static void Main(string[] args)
    {
        List<BaseT> items = new List<BaseT>() {new DerivedA(), new DerivedB()};
        var generator = new DerivedGenertor();
        generator.Generate(items);
    }
}

这是另一个更明显的例子：

class BaseT
{}

class DerivedA : BaseT
{}

class DerivedB : BaseT
{}

class DerivedC : BaseT
{ }

class Generator
{
    public void Generate(IEnumerable<BaseT> objects)
    {
        string str = "";
        foreach (dynamic item in objects)
        {
            str = str + this.Generate(item); //throws an exception on third item
        }
    }

    public virtual string Generate(DerivedA a)
    {
        return " A ";
    }

    public virtual string Generate(DerivedC c)
    {
        return " C ";
    }
}

class DerivedGenertor : Generator
{
    public virtual string Generate(DerivedB b)
    {
        return " B ";
    }
}



class Program
{
    static void Main(string[] args)
    {
        List<BaseT> items = new List<BaseT>() {new DerivedA(), new DerivedC(), new DerivedB()};
        dynamic generator = new DerivedGenertor();
        generator.Generate(items);
    }
}

解决方法:

您还需要将Generator声明为动态,以便对输入对象和被调用的方法进行动态分辨.但是您必须将访问修饰符更改为public或protected internal才能执行此操作,因为您现在拥有一个外部解析的方法.

class BaseT
{ }

class DerivedA : BaseT
{ }

class DerivedB : BaseT
{ }

class Generator
{
    public string Generate(IEnumerable<BaseT> objects)
    {
        string str = "";
        dynamic generator = this;
        foreach (dynamic item in objects)
        {
            str = str + generator.Generate(item); 
        }
        return str;
    }

    protected internal virtual string Generate(DerivedA a)
    {
        return " A ";
    }
}

class DerivedGenertor : Generator
{
    protected internal virtual string Generate(DerivedB b)
    {
        return " B ";
    }
}



class Program
{
    static void Main(string[] args)
    {
        List<BaseT> items = new List<BaseT>() { new DerivedA(), new DerivedB() };
        var generator = new DerivedGenertor();
        string ret = generator.Generate(items);
    }
}

标签：c,dynamic,late-binding
来源： https://codeday.me/bug/20190519/1136740.html