Can't understand the Exception when using dynamic with generic collection in .net4

Question

check the code below please:

static void Main(string[] args) {
    IList<dynamic> items = new List<dynamic>();
    items.Add(3);
    items.Add("solid");
    dynamic i = new ExpandoObject();
    items.Add(i); //System.Collections.Generic.IList<object>' does not contain a definition for 'Add'
    Console.WriteLine();
}

is this a bug in "dynamic" mechanism?

+1 wish I knew more about the complexity of the dynamic binding. I just tried this and it appears that `items.Add(new ExpandoObject());` is fine, but `items.Add((dynamic)new ExpandoObject());` is not. — Daniel Earwicker, Nov 03 '11 at 14:30

score 3 · Accepted Answer · answered Nov 03 '11 at 14:35

3

Looks like a bug (or is it a feature request?):

https://connect.microsoft.com/VisualStudio/feedback/details/534288/ilist-dynamic-cannot-call-a-method-add-without-casting

answered Nov 03 '11 at 14:35

Daniel Earwicker

114,894
38
205
284

score 3 · Answer 2 · answered Apr 02 '12 at 17:25

3

This should do the trick:

static void Main(string[] args) {
    IList<dynamic> items = new List<dynamic>();
    items.Add(3);
    items.Add("solid");
    dynamic i = new ExpandoObject();
    items.Add((object) i); // type-cast dynamic object
    Console.WriteLine();
}

answered Apr 02 '12 at 17:25

JoBot

131
1
7

Thx，trick works fine,but I like simplicity and explicitness than trick in my code :) – Inside Apr 09 '12 at 00:58

Can't understand the Exception when using dynamic with generic collection in .net4

2 Answers2

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