C# Dynamic - "RuntimeBinderException"

Question

I am initializing dynamic with ExpandoObject and adding some items to it.

        dynamic dy = new System.Dynamic.ExpandoObject();
        dy.Property2 = new List<string>();
        dy.Property2.Add("Two");
        dy.Property2.Insert(0, "Zero");
        var coll1 = (List<string>)dy.Property2;
        var element = coll1.ElementAt(0);

above code works fine. but exception is thrown if replace last two statement with code mention below

        var data = dy.Property2.ElementAt(0);

exception is 'System.Collections.Generic.List' does not contain a definition for 'ElementAt'

Answer 1

And it's absolutely right - List<T> doesn't have an ElementAt method. It only works in your original code because it's an extension method on IEnumerable<T>. Dynamic typing doesn't let you call extension methods using the "special" syntax - but you can call it as a normal static method call:

var data = Enumerable.ElementAt(dy.Property2, 0);