为什么“（（dynamic）dictionary）.MyKey”抛出RuntimeBinderException？

Question

Let's imagine this simple snippet:

Dictionary<string,string> dictionary = new Dictionary<string, string>();
dictionary.Add("MyKey", "MyValue");

string val;
dictionary.TryGetValue("MyKey", out val);
Console.WriteLine(val); // print "MyValue"

Console.WriteLine(((dynamic)dictionary).MyKey); // throws a RuntimeBinderException

Why a RuntimeBinderException is thrown at last line?

Thanks for your help!

Answer 1

Because Dictionary<string, string> does not have a member MyKey . Dynamic typing does not create members on the fly.

To put it in perspective, what you're trying to do is equivalent to ((dynamic) dictionary).get_MyKey() . Clearly, the dictionary does not have a get_MyKey() method.