Yes - or you can cast it to object - or use Console.WriteLine instead and get the same result:

dynamic x = new ExpandoObject();
x.Name = "Mario";
x.Age = 23;
((object)x).Dump();
Console.WriteLine (x); // same result

You can cast it to IDictionary<string,object> before dumping it.
For instance:

dynamic x = new ExpandoObject();
x.Name = "Mario";
x.Age = 23;
((IDictionary<string,object>)x).Dump();