Object Orientation in .NET ( has anyone at Microsoft heard of it ? )

It's not uncommon to be working with code and want to call an event explicitly. In this case, classes derived from the EventArgs class, have an Empty property, which returns an empty instance, useful for doing exactly that, without having to construct an object we will not use. However, while it's possible to use the 'new' keyword to override a property, doing MyMethod(this, RoutedEventArgs.Empty); returns a compiler error, as the Empty propertly returns EventArgs, not RoutedEventArgs. In other words, while RoutedEventArgs in particular represents a class where you are very likely to not examine the event arguments, you still cannot use the property, it is worthless.

This is true of ALL derived classes of EventArgs, although I can see how, for example, a mouse related event args can be assumed to contain data you need ( although this is often not true, if I handle the mouse left button click event, I don't often care about anything passed in ) The only place I can think of where this is almost sure to not be the case, is keyboard events, where usually I want to know what key was pressed. It is for this reason that I've never tried to use KeyEventArgs.Empty, that is, assuming I were to forget that the construct as a whole is useless.

In the same way when I use Bitmap.FromFile in C# in general, I need to cast the Image that is returned, to a Bitmap. This is because it's calling a base method, I guess. That makes sense, but then why not make the base method return a Bitmap, given that you can't alter a method by return type, however, if I called Image.FromFile and got back a Bitmap, I could quite happily assign the value to an Image, and it would downcast. In fact, all things being equal, it's possible that the class always returns a Bitmap, but always specifies an Image as the return type.

Yes, I am right. The Image.FromFile ultimately calls this:

internal static Image CreateImageObject(IntPtr nativeImage) { int type = -1; int status = SafeNativeMethods.Gdip.GdipGetImageType (new HandleRef(null, nativeImage), out type); if (status != 0) { throw SafeNativeMethods.Gdip.StatusException(status); } switch (((ImageTypeEnum) type)) { case ImageTypeEnum.Bitmap: return Bitmap.FromGDIplus(nativeImage); case ImageTypeEnum.Metafile: return Metafile.FromGDIplus(nativeImage); } throw new ArgumentException(SR.GetString("InvalidImage")); }

As an aside, surely this code would be prettier if the exception came from a default case, instead of just sitting underneath like that. Do they have coding standards in Redmond ? In fairness, if my suggestion would compile at all, I am pretty sure that it didn't work in early versions at least, b/c the compiler could not work out that every case had a return value. So, perhaps this code has just not been looked at in a long time.

The return type here is an Image. Bitmap.FromGDIplus looks like this:

internal static Bitmap FromGDIplus(IntPtr handle) { Bitmap bitmap = new Bitmap(); bitmap.SetNativeImage(handle); return bitmap; }

So, in a nutshell, even if I am using an Image, I get sent a Bitmap, but if I am using a Bitmap, or an Image, either way, the object is downcast to an Image for no good reason that I can see, before I get it back. No memory is saved, all that happens, is another reason for a meaningless cast.

Bitmap bm = (Bitmap) Bitmap.FromFile(@"c:\Image.jpg");

Is that really the best we can do ?