ADD THE PHOTOS IN AN ALBUM TO THE LIST

This code initializes the control with the contents of the open album. Note in particular how we define the Tag property to hold the integer index. Since the Tag property holds an object instance, this line boxes the integer value in order to store it as a reference type. Boxing was mentioned in chapter 5, and is discussed in detail in appendix A.

You can compile and run this code if you like. Double-click on an album to activate it and display the contained photographs. Most of the support for photographs is still missing, so you’ll find it rather easy to cause an error.

The remainder of this section implements the support required for both albums and photographs to coexist in our ListView control. We begin with column sorting.

14.5.4SORTING A COLUMN (AGAIN)

Our users will want to sort the columns for both the album and photograph display, so we need to make some changes in our MyListViewComparer class to enable this support. Of key importance is the ability to tell which type of object we are comparing. When comparing photos, we also need to know the PhotoAlbum they come

from. We can handle both requirements through a private album field. When the album is null, we are comparing PhotoAlbum objects. When an album is assigned, we are comparing Photograph instances.

Let’s add this field and update our Compare method to make use of this value.

IDENTIFY THE TYPE OF OBJECT TO COMPARE

Now all we have to do is implement the ComparePhotos method to compare two Photograph items. Much of this will be similar to the CompareAlbums method. The one difference is when we need to compare items using the Taken column. This column holds a date value, so a string comparison is not appropriate. It turns out the DateTime structure provides a Compare method for just this purpose.

We can use this method in the ComparePhotos method to our comparer class.

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IMPLEMENT METHOD TO COMPARE TWO PHOTO ITEMS

The last change required for column sorting is to update the CurrentAlbum property for our comparer field whenever the contents of the ListView control are refreshed. This ensures that our Compare implementation performs the proper comparison based on the contents of the control.

UPDATE THE CURRENTALBUM PROPERTY WHEN REQUIRED

UPDATE THE CURRENTALBUM PROPERTY WHEN REQUIRED (continued)

Our application can now sort both photographs and albums. Once again you can compile and run the program if you are careful not to use any photograph functionality we have not yet implemented. Our next task is the Properties dialog.

14.5.5UPDATING THE PROPERTIES MENU

You may think we are moving through this code rather quickly, and you would be right. While these changes are required as a result of our defined item activation behavior, there are not a lot of new concepts to cover. This is especially true here. As a result, we will simply run through the steps in the following table and then move on to our final topic of editing the item label.

UPDATE THE CLICK HANDLER FOR THE PROPERTIES MENU