Question

I have a class with an IList readonly property. I have created a simple extension method, AddCSV, to add multiple items to that list. I want to create an action delegate to populate the list via the extension method. So far, I have

private Action<TListPropertyContainer, TDataValue> CreateListPropertySetter<TListPropertyContainer, TDataValue>(string listName)
{
    var list = typeof(TListPropertyContainer).GetProperty(listName);
    var method = typeof(Extensions).GetMethod("AddCSV");
    return (Action<TListPropertyContainer, TDataValue>)Delegate.CreateDelegate(typeof(Action<TListPropertyContainer, TDataValue>), list, method);
}

but obviously this isn’t working!

I am aware that there are other options. For example
a) I could inherit the list into my own customer class and add the AddCSV there
b) I could make items property read/write and set a fully populated list into my class

I’d be grateful if someone could correct me.

Many thx

Simon

Answer 1

There are two main problems.

1. You are trying to invoke the method on a PropertyInfo, not a list. To get the value of the property you would need to make a call to GetValue()

2. The call to GetMethod() doesn’t specify binding flags. I suspect it might work better with GetMethod("AddCSV", BindingFlags.Public | BindingFlags.Static).

That being said, why are you instantiating it reflectively when you know the type and the method beforehand? It seems like you could just do:

 private Action<TListPropertyContainer, TDataValue> CreateListPropertySetter<TListPropertyContainer, TDataValue>(string listName)
 {
       var propertyInfo = typeof(TListPropertyContainer).GetProperty(listName);
       return (container,value) => {
            var list = (IList<TDataValue>)propertyInfo.GetValue(container,null);
            list.AddCSV(list);
       };
  }

If I am making incorrect assumptions about the signature of the extension method or the type of property, you can still do it with Delegate.CreateDelegate(), but take the comments about the PropertyInfo and the BindingFlags into account