REIMPLEMENT THE ITEMACTIVATE EVENT HANDLER (continued)

Our two view controls are now totally in sync with each other. The appropriate tree node is always selected, and as a result the contents of the list view are updated as required.

15.5FUN WITH TREE VIEWS

There are a few loose ends to tie up in our application. In this section we look at additional uses for a tree view class in order to complete the functionality required in the MyAlbumExplorer application. This section is to demonstrate various features and functionality, rather than explain additional Windows Forms concepts. As a result, this section will be short on discussion and simply present the code required to make the described changes.

There are three changes we will make here:

1Display the image associated with a selected photograph node.

2Permit the label text for a node to be edited.

3Display the album or photo property dialog associated with a node.

We will discuss these topics in the order they appear in this list.

15.5.1DISPLAYING THE PHOTOGRAPH

Our first topic is displaying the photograph when a photograph node is selected in the tree view. You might think that we could draw directly on the ListView control. In fact, the ListView class does not permit the Paint event to be handled by an instance of the class. So an alternate approach is required.

Instead, we will use a PictureBox control for this purpose. Since the PictureBox control does not support a proper aspect ratio for its contained image, we will

handle the Paint event and draw the image manually. This is shown in figure 15.9. When a list of albums or photographs is displayed, we will hide the picture box control. Conversely, when a photograph is displayed, we will hide the list view control.

Figure 15.9

Normally a PictureBox control appears with standard control colors. Since this PictureBox appears in place of a ListView control, we will use standard window colors instead.

The following table details the steps necessary to add this feature to our interface.

Set the version number of the MyAlbumExplorer application to 15.4.

DISPLAY PHOTOGRAPH IN A PICTUREBOX CONTROL

DISPLAY PHOTOGRAPH IN A PICTUREBOX CONTROL (continued)

DISPLAY PHOTOGRAPH IN A PICTUREBOX CONTROL (continued)

As we mentioned at the start of this section, we will not spend much time discussing these changes, since they leverage concepts and features we have seen before. Let’s move on to editing a tree node’s label.

15.5.2SUPPORTING LABEL EDITS

Tree nodes can be edited in a manner similar to list items. There is a BeginEdit method in the TreeNode class to initiate a label edit programmatically, and Befor-

eLabelEdit and AfterLabelEdit events in the TreeView class that occur before and after the user edits the label. Event handlers for these events receive the belEditEventArgs class for the event parameter. This class is summarized in

.NET Table 15.5, and is manipulated in much the same way as we saw for the LabelEditEventArgs class when handling label events for the ListView class.