如何覆盖动态对象属性的获取访问器

Question

假设我有以下课程：

public class Person {
    public string Name { get; set; }
    public string Surname { get; set; }
    public string FullName {
        get {
            return Name + " " + Surname;
        }
    }
}

以下块：

Person person = new Person();
person.Name = "Matt";
person.Surname = "Smith";
return person.FullName;

将返回Matt Smith。

让我们将Person 类型更改为动态ExpandoObject。

代码如下所示：

dynamic person = new ExpandoObject();
person.Name = "Matt";
person.Surname = "Smith";

但这就是我卡住的地方。如何覆盖新 FullName 属性的 get 访问器？

我可以创建一个新方法来达到同样的效果：

person.GetFullName = (Func<string>)(() => {
      return person.Name + " " + person.Surname;
});

但这最终会是一个方法而不是一个属性，因此这样称呼它：

person.GetFullName();

---

编辑

请注意，我不想知道如何定义或创建新的动态属性。我想知道如何覆盖或定义动态属性的 get 访问器。

我想象的代码可以是这样的：

person.FullName.get = (Func<string>)(() => {
     return person.Name + " " + person.Surname;
});

然后，像这样调用：

Console.WriteLine(person.FullName); //Prints out "Matt Smith"

Answer 1

dynamic person = new GetterExpando();
person.Name = "Matt";
person.Surname = "Smith";
person.FullName = new GetterExpando.Getter(x => x.Name + " " + x.Surname);

Console.WriteLine(person.FullName);  // Matt Smith

// ...

public sealed class GetterExpando : DynamicObject
{
    private readonly Dictionary<string, object> _data = new Dictionary<string, object>();

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        _data[binder.Name] = value;
        return true;
    }

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        object value;
        if (_data.TryGetValue(binder.Name, out value))
        {
            var getter = value as Getter;
            result = (getter == null) ? value : getter(this);
            return true;
        }
        return base.TryGetMember(binder, out result);
    }

    public delegate object Getter(dynamic target);
}

Answer 2

public class SampleDynamicObject : DynamicObject
{
    Dictionary<string, Func<dynamic, object>> customFieldHandlers = new Dictionary<string, Func<dynamic, object>>();

    Dictionary<string, object> values = new Dictionary<string, object>();

    public void Get(string property, Func<dynamic, object> handler)
    {
        customFieldHandlers.Add(property, handler);
    }

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        if (customFieldHandlers.ContainsKey(binder.Name))
        {
            result = customFieldHandlers[binder.Name](this);
            return true;
        }

        result = values[binder.Name];
        return true;
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        values[binder.Name] = value;
        return true;
    }
}


dynamic sampleObject = new SampleDynamicObject();

        sampleObject.Get("FullName", (Func<dynamic, object>)((o) => 
        {
            dynamic obj = o;
            return o.Name + " " + o.Surname; 
        }));

Answer 3

试试看

 public class MyDynamic : DynamicObject
{
    private Dictionary<string,object> obj = new Dictionary<string, object>();
    public Func<string,dynamic,object> PropertyResolver { get; set; }
    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        if (obj.ContainsKey(binder.Name))
        {
            result =  obj[binder.Name];
            return true;
        }

        if (PropertyResolver != null)
        {
            var actResult = PropertyResolver(binder.Name, this);
            result = actResult;
            return true;
        }

        return base.TryGetMember(binder, out result);
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        obj[binder.Name] = value;
        return true;
    }
}

 static void Main(string[] args)
    {
        dynamic person = new MyDynamic();
        person.Name = "Matt";
        person.Surname = "Smith";
        person.PropertyResolver = (Func<string, dynamic, object>)
            ((string name, dynamic me) => { return name == "FullName" ? me.Name + me.Surname : "";  });
Console.WriteLine(person.FullName);
}

Answer 4

public class SampleDynamicObject : DynamicObject
{
    Dictionary<string, object> values = new Dictionary<string, object>();

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        if (binder.Name == "Fullname")
        {
            result = values["Name"] + " " + values["Surname"];
            return true;
        }

        result = values[binder.Name];

        return true;
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        values[binder.Name] = value;
        return true;
    }
}