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'

Jon Skeet · Accepted Answer · 2014-08-04 14:26:19Z

5

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);

answered Aug 4, 2014 at 14:26

Jon Skeet

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3 Comments

slash shogdhe Over a year ago

On MSDN for dynamic its written " The type is a static type, but an object of type dynamic bypasses static type checking. In most cases, it functions like it has type object" Can you please explain, need to understand ??

Jon Skeet Over a year ago

@slashshogdhe: Not in a comment thread, no. There's a huge amount to be said about dynamic (I wrote a whole chapter on it in C# in Depth) - it's really not appropriate to go into details within comments.

slash shogdhe Over a year ago

Placed a question on stackoverflow, please help now.

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