Easy creation of properties that support indexing in C#

In C# I find indexed properties extremely useful. For example:

var myObj = new MyClass();
myObj[42] = "hello"; 
Console.WriteLine(myObj[42]);

However as far as I know there is no syntactic sugar to support fields that themselves support indexing (please correct me if I am wrong). For example:

var myObj = new MyClass();
myObj.field[42] = "hello"; 
Console.WriteLine(myObj.field[42]);

The reason I need this is that I am already using the index property on my class, but I have GetNumX(), GetX(), and SetX() functions as follows:

public int NumTargetSlots {  
    get { return _Maker.NumRefs; }  
}
public ReferenceTarget GetTarget(int n) {
    return ReferenceTarget.Create(_Maker.GetReference(n));
}
public void SetTarget(int n, ReferenceTarget rt) {
    _Maker.ReplaceReference(n, rt._Target, true);
}

As you can probably see exposing these as one indexable field property would make more sense. I could write a custom class to achieve this every time I want the syntactic sugar but all of the boilerplate code just seem unnecessary.

So I wrote a custom class to encapsulate the boilerplate and to make it easy to create properties that can be indexed . This way I can add a new property as follows:

public IndexedProperty<ReferenceTarget> TargetArray  {
    get { 
       return new IndexedProperty<int, ReferenceTarget>(
           (int n) => GetTarget(n), 
           (int n, ReferenceTarget rt) => SetTarget(n, rt));
       }
}

The code for this new IndexedProperty class looks like:

public class IndexedProperty<IndexT, ValueT>
{
    Action<IndexT, ValueT> setAction;
    Func<IndexT, ValueT> getFunc;

    public IndexedProperty(Func<IndexT, ValueT>