ADD THE SUBITEMS FOR EACH ITEM IN THE LIST

Compile and run your code to ensure that it works. When you look at the Details view, note how the width of each column can be adjusted by clicking on the vertical line between two columns and dragging it to the left or right.

Congratulations, you have just completed your first list view! Your life may never be the same. Before you go off and celebrate, there is one other topic related to columns that is worth some discussion.

14.3.3SORTING A COLUMN

It is typical in applications such as Windows Explorer to sort the contents of a List-

View control column whenever a column title is clicked. The first time the title is clicked, the items are sorted based on the column’s contents in ascending order, or a to z order for strings; and a second click sorts in descending, or z to a, order. Whether to support this behavior in your applications depends on the nature of the application and the user environment for which it is targeted. Many Windows users expect such behavior, and may find it odd if an application does not support this feature. In this section we look at how to support this feature in Windows Forms applications, using our MyAlbumExplorer application as an example.

The ListView class provides three members of particular importance when you wish to support sorting in the Details view.

•The Sorting property defines how the items are initially sorted. This is a SortOrder enumeration value, one of None for no sorting, Ascending, or Descending. This defaults to None, which is why our application currently

displays the items in random order.

•The ColumnClick event occurs when a column is clicked. This is used to modify the control’s sorting behavior as appropriate for the selected column. Event handlers for this event receive a ColumnClickEventArgs parameter that contains a Column property indicating the column header clicked by the user.

•The ListViewItemSorter property defines the IComparer interface used to compare two ListViewItem objects for the list. An overview of the IComparer interface is given in .NET Table 14.6.

We will use each of these members to define the sorting behavior for our application. We will define a class supporting the IComparer interface first, and then use this class to implement a ColumnClick event handler.

.NET Table 14.6 IComparer interface

The IComparer interface is an interface for comparing two objects, and is part of the Systems.Collections namespace. This namespace also provides two implementations of this interface for comparing string objects. The Comparer class supports case-sensitive comparisons, while the CaseInsensitiveComparer class supports case-insensitive comparisons. Both of these classes provide a Default property that returns an initialized instance of the class.

For a ListView object, the comparison interface must accept two ListViewItem objects and return an appropriate value depending on the current column and sorting order. The ListView object itself defines the current sorting order based on the Sorting property value. We will need to keep track of the current column as part of our IComparer implementation.

We will begin by implementing a comparison class within our MainForm definition. We will use the rather noncreative name MyListViewComparer for this class.

To avoid hard-coding integer values into our code, the following steps also define constants for the column indices.

DEFINE A COMPARER CLASS FOR THE LIST VIEW

DEFINE A COMPARER CLASS FOR THE LIST VIEW (continued)