New DynamicObject In .NET 4.0

Microsoft has released SharePoint 2010 Beta2 and .NET 4.0 Beta2 recently (Ironically SharePoint 2010 is still based on .NET 3.5).

The new Dynamic type in .NET 4.0 looks quite interesting. Not like .NET 3.5 dynamic variable (var keyword) which is static type inference by compiler, Dynamic objects are run-time behavior. Following code example is copied from MSDN documentation, and comments are removed for brevity reason:

using System;
using System.Collections.Generic;
using System.Dynamic;

public class DynamicDictionary : DynamicObject
{
    Dictionary<string, object> dictionary = new Dictionary<string, object>();
    public int Count { get { return dictionary.Count; }}

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        string name = binder.Name.ToLower();
        return dictionary.TryGetValue(name, out result);
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        dictionary[binder.Name.ToLower()] = value;
        return true;
    }
}

class Program
{
    static void Main(string[] args)
    {
        dynamic person = new DynamicDictionary();
        person.FirstName = "Ellen";
        person.LastName = "Adams";

        Console.WriteLine(person.firstname + " " + person.lastname);
        Console.WriteLine( "Number of dynamic properties:" + person.Count);
        Console.Read();
    }
}

The result is:

Ellen Adams
Number of dynamic properties:2