通过system.Reflection使用'path'访问基类成员

Question

So I have something like this:

using System.Reflection;

public class SomeFieldsGrouped{
    public int foo;
    public string bar;
    //<etc>
}

public class A{
    public SomeFieldsGrouped someFieldsGroupedInA; 
    //<etc>
}
public class B : A{
    public int ffo;
    //<etc>
}

public class YetAnotherClass
{
    public B b; //Instantiated and stuff
    public string bbr = "someFieldsGroupedInA.foo";

    public static object GetPropertyValue (object o, string path)
        {
            object value = o;
            string[] pathComponents = path.Split (new char[]{'.'}, StringSplitOptions.RemoveEmptyEntries);
            if (pathComponents.Length == 1) {
                return value.GetType ().GetField (pathComponents [0]).GetValue (o);
            }
            foreach (var component in pathComponents) {
                value = value.GetType ().GetProperty (component).GetValue (value, null);//this is where it stops everytime
            }
        return value;
    }

    public void Main(){
        object o = GetPropertyValue(b, bbr); //where is your god now?
    }
}

(keep in mind its not actual code)

What I'm trying to accomplish is to make a method based off Reflection, with which I can access ANY property with path as a string. Now this is a fun thing that happens here, I should be able to access "someFieldsGroupedInA", as it's base class member. And I can do so with b.SomeFieldsGroupedInA, but why can't I with Reflection?

And if anybody can show me general direction where can I find something like the thing I'm gonna write, as its gonna be extremely hard for me to make something that would work with arrays and other stuff, I'd be really thankful.

Answer 1

One problem with your code is that you are defining fields in your classes, but when you try to access them you use GetProperty instead of GetField .

To fix it, replace this code (in the loop):

value = value.GetType().GetProperty (component).GetValue (value, null);

With this code:

value = value.GetType().GetField(component).GetValue(value);

If the path could specify properties and/or fields, then you should make your code check to see if there is a property with the specific name. If it does not find it, it checks to see if there is a field with such name.

Better yet, as @Silvermind said, it is better to use properties instead of fields. Here is how your classes would look like:

public class SomeFieldsGrouped{
    public int foo {get;set;}
    public string bar {get;set;}
    //<etc>
}

public class A{
    public SomeFieldsGrouped someFieldsGroupedInA {get;set;} 
    //<etc>
}

public class B : A{
    public int ffo {get;set;}
    //<etc>
}

And your method would look like this:

public static object GetPropertyValue (object o, string path)
{
    object value = o;
    string[] pathComponents = path.Split (new char[]{'.'}, StringSplitOptions.RemoveEmptyEntries);
    if (pathComponents.Length == 1) {
        return value.GetType().GetProperty(pathComponents [0]).GetValue (o, null);
    }
    foreach (var component in pathComponents) {
        value = value.GetType().GetProperty (component).GetValue (value, null);
    }
    return value;
}