14.5.7REDISPLAYING THE ALBUMS

As a final change, we need to give our user the opportunity to redisplay the album view. We may as well provide a menu to display the photo view as well, as an alternative to double-clicking on the album.

ALLOW USER SELECTION OF THE KIND OF OBJECT TO DISPLAY

14.6RECAP

This completes our discussion of the ListView class. In this chapter we discussed list views in detail, and created a new MyAlbumExplorer interface to display the collection of albums available in our default album directory. We supported all four possible views available in a ListView control, and provided support for column

sorting, item selection, and label editing. We finished by implementing this same support for the photos in an album, so that our application can display albums or photographs in the control.

Along the way we looked at a number of classes provided to support this control, most notably the ListViewItem, ListViewItem.ListViewSubItem, and ColumnHeader classes. We also examined the IComparer interface as a way to define how two objects should be compared, and implemented a class supporting this interface in order to sort the columns in our detailed view of the list.

The next chapter looks at a close cousin to the ListView class, namely the

TreeView control.

Tree views

In the previous chapter we created the MyAlbumExplorer application incorporating a ListView control. This program presents the default set of photo albums available and the collection of photographs contained within these albums.

In this chapter we extend this program to include a TreeView control in order to present a more traditional explorer-style interface. Specific topics we will cover in this chapter include the following:

•Exploring the TreeView class.

•Using the Splitter control to divide a container.

•Populating a tree with the TreeNode class, both in Visual Studio and programmatically.

•Selecting nodes in a tree.

•Editing the labels for a tree.

•Integrating a ListView and TreeView control into an application.

As we did for list views, we begin this chapter with a general discussion of tree views and a discussion of the terms and classes used for this control.

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15.1TREE VIEW BASICS

The TreeView class is a close cousin of the ListView class. List views display a collection as a list, while tree views display collections as a tree. Each item in a tree view is called a tree node, or just a node. Tree nodes can contain additional nodes, called child nodes, to arbitrary levels in order to represent a hierarchy of objects in a single control. Various elements of a TreeView control are illustrated in figure 15.1.

Figure 15.1 The TreeView control automatically shows the entire label in a tool tip style format when the mouse hovers over a node, as was done for the “From the Walking Path” entry in this figure.

The explorer-style interface shown in the figure and used by other applications such as Windows Explorer is a common use of the TreeView and ListView classes. In this chapter we build such an interface by extending the MyAlbumExplorer project constructed in chapter 14.

15.2THE TREEVIEW CLASS

The TreeView class is summarized in.NET Table 15.1. Like the ListView class, this class inherits directly from the Control class, and provides an extensive list of members for manipulating the objects displayed by the tree.

.NET Table 15.1 TreeView class

The TreeView class represents a control that displays a collection of labeled items as a treestyle hierarchy. Typically an icon is displayed for each item in the collection to provide a graphical indication of the nature or purpose of the item. Items in the tree are referred to as nodes, and each node is represented by a TreeNode class instance. This class is part of the System.Windows.Forms namespace, and inherits from the Control class. See .NET Table 4.1 on page 104 for a list of members inherited by this class.

A TreeView object is created much like any other control in Visual Studio .NET: you simply drag the control onto the form. In our MyAlbumExplorer application, we already have a ListView on our form, so it looks like all we need to add is a tree view in order to support the interface shown in figure 15.2.