Archive for September, 2010

Programming languages evolve rapidly. New great features have been added to one of my favorite languages C# – lambda expressions, extension methods, dynamic type and many others. What can we expect next?

One thing that comes to mind is a more advanced property system. WPF introduced a notion of DependencyProperty which has proved its success. But.. can C# support something similar natively – properties which could store their states and dynamic meta data in addition to plain values? Why not?

Consider the following code sample:

// A product type in this sample has a property Name of type String
var product = new Product();

// This will print "Product.Name.IsDirty: False"
Console.WriteLine("Product.Name.IsDirty: {0}", product.Name.IsDirty);

// Subscribe to an event
product.Name.BeforeChange += (s, e) => {
		if (e.NewValue == "C++") { e.Cancel = true; }
	};

// Now let's try to update product's Name property
product.Name = "C# 4.0 in a Nutshell";

// And now this will print "Product.Name.IsDirty: True"
Console.WriteLine("Product.Name.IsDirty: {0}", product.Name.IsDirty);

// Then when you try to save this product in database, it will be easier
// for your Store Repository to decide which fields must be saved
// and which can be skipped
storeRepository.Add(product);
storeRepository.SubmitChanges();

So far so good? But.. how this Product class is implemented? Actually not a magic.

Here is one of possible implementations – Codename “Properties inside properties” or “Nested Properties” in short:

public interface IProduct
{
	string Name { get; set; bool IsDirty { get; } }
}

public class Product : IProduct
{
	private string name;
	private bool nameIsDirty;

	public string Name
	{
		get { return name; }
		set { if (name != value) { name = value; nameIsDirty = true; } }
		bool IsDirty { get { return nameIsDirty; } }
	}
}

Happy coding!

P.S.: To tell you the truth, this is not the brightest example of what to expect in the next version of C#. But if this blog post motivated you to creative thinking – then my goal is completed. Don’t be afraid to innovate; be different!