Question

In my code, I declare one ArrayList within a ParentClass

public class ParentClass {
...
public ArrayList hybridElem; 
...

and then using Reflection that runs off the ParentClass, I am able to successfully obtain FieldInfo for this ArrayList @ runtime.

Using that FieldInfo, I want to be able to add or read elements from the hybridElem.
I am able to obtain all relevant PropertyInfo of ArrayList such as .Item, .Count, .ToArray etc etc … and also obtain getters and setters for these properties.

Unfortunately, none of them are being successfully invoked because MethodInfo.Invoke expects Object reference to ArrayList

Any Solutions?

Answer 1

You can do it easily enough. However, as the comments rightfully stated, I suggest you to switch from ArrayList to a generic collection.

var instance = new ParentClass();
var fieldInfo = instance.GetType().GetProperty("MyList");
var arrayList = fieldInfo.GetValue(instance) as ArrayList;
var count = arrayList.Count;

With:

public class ParentClass
{
    public ArrayList MyList { get; set; }

    public ParentClass()
    {
        MyList = new ArrayList();
    }
}

Alternatively, to adapt it to your class which uses a field (assuming that said field is initialized somewhere):

var instance = new ParentClass();
var fieldInfo = instance.GetType().GetField("hybridElem");
var arrayList = fieldInfo.GetValue(instance) as ArrayList;
var count = arrayList.Count;