How to create own dynamic type or dynamic object in C#?

Question

There is, for example, the ViewBag property of ControllerBase class and we can dynamically get/set values and add any number of additional fields or properties to this object, which is cool. I want to use something like that, beyond MVC application and Controller class in other types of applications. When I tried to create dynamic object and set its property like this:

1. dynamic MyDynamic = new { A="a" };
2. MyDynamic.A = "asd";
3. Console.WriteLine(MyDynamic.A);

I've got RuntimeBinderException with message Property or indexer '<>f__AnonymousType0.A' cannot be assigned to -- it is read only in line 2. Also, I suspect it's not quite what I'm looking for. Maybe is there some class which allows me to do something like:

??? MyDynamic = new ???();
MyDynamic.A = "A";
MyDynamic.B = "B";
MyDynamic.C = DateTime.Now;
MyDynamic.TheAnswerToLifeTheUniverseAndEverything = 42;

with dynamic adding and setting properties.

Answer 1

dynamic MyDynamic = new System.Dynamic.ExpandoObject();
MyDynamic.A = "A";
MyDynamic.B = "B";
MyDynamic.C = "C";
MyDynamic.Number = 12;
MyDynamic.MyMethod = new Func<int>(() => 
{ 
    return 55; 
});
Console.WriteLine(MyDynamic.MyMethod());

Read more about ExpandoObject class and for more samples: Represents an object whose members can be dynamically added and removed at run time.