Question

I have some intialized Property/Fields that are “constant” and I want to know which one of the following line is the best to use :

1. public static Color MyColor { get { return Color.Red; } }
2. public static readonly Color MyOtherColor = Color.Red;

Is there some runtime differences after (lazy)initialization ?
Are the performance usages differents ?

Answer 1

The Field usage guidelines recommend using public static read-only fields for predefined object instances. For example:

public struct Color
{
    // this is a predefined immutable instance of the containing Type
    public static readonly Color Red = new Color(0x0000FF);

    ...
}

In your case, I’d probably use a property:

public class MyClass
{
    // Not a predefined instance of the containing Type => property
    // It's constant today, but who knows, tomorrow its value may come from a 
    // configuration file.
    public static Color MyColor { get { return Color.Red; } }
}

UPDATE

It’s crystal clear when I see your answer, but using ILSpy in System.Drawing shows me the following code: public static Color Red { get { return new Color(KnownColor.Red); } }

The guidelines linked above (which use Color as an example) are for .NET 1.1 and have possibly evolved. Personally I don’t think you can go wrong by using a property. .NET 4.0 Field Guidelines are similar, but use DateTime.MaxValue and DateTime.MinValue as examples of predefined object instances.