Use Reflection to call Cast fails with Parameter count mismatch exception

I have collection of type Foo. It is bind to a RadGridView's ItemsSource. I want to get all current items from RadGridView using below code -

var current_collection = gv.Items.Cast<Foo>().ToArray();

I want to do the above dynamically using reflection, but having trouble making it run, below is my code so far -

var t = gv.ItemsSource.GetType().GetGenericArguments().Single();

Here t is Foo type.

var x = typeof(Enumerable).GetMethod("Cast").MakeGenericMethod(t).Invoke(gv.Items, null);