To create an ImageList at design time, drag it onto your form (it will appear in the component tray). The basic properties for the ImageList are described in Table 6-1.

You can add, remove, and rearrange images using the ListView designer. Just click the ellipsis ( … ) next to the Images property in the Properties window. Images can be drawn from almost any common bitmap file, including bitmaps, GIFs, JPEGs, and icons. When you add a picture, some related read-only properties about its size and format appear in the window (see Figure 6-1).

Figure 6-1: The ImageList designer

Dealing with the ImageList in Code

If you look at the automatically generated code, you'll see that the image files you add are stored in a resource file in your project (as is any binary data added at design time). When the form is loaded, the images are deserialized into Image objects and placed in the collection. A special class, the ImageListStreamer, makes this process a simple one-line affair, regardless of how many images are in your ImageList. This code is inserted automatically by VS .NET, and doesn't need to be modified manually

this.imagesLarge.ImageStream = ((System.Windows.Forms.ImageListStreamer) (resources.GetObject("imagesLarge.ImageStream")));

If you want to have an ImageList object around for a longer period (for example, to use in different forms), you should create it directly in code. You might also want to create Image objects out of graphic files rather than use a project resource.

First, you need a variable to reference the ImageList.

private ImageList iconImages = new ImageList();

Then, you can create a method that fills the ImageList.

// Configure the ImageList. iconImages.ColorDepth = System.Windows.Forms.ColorDepth.Depth8Bit; iconImages.ImageSize = new System.Drawing.Size(16, 16); // Get all the icon files in the current directory. string[] iconFiles = Directory.GetFiles(Application.StartupPath, "*.ico"); // Create an Image object for each file and add it to the ImageList. // You can also use an Image subclass (like Icon). foreach (string iconFile in iconFiles) { Icon newIcon = new Icon(iconFile); iconImages.Images.Add(newIcon); }

Once you have images in an ImageList control, you can use them to provide pictures to another control. Many modern controls provide an ImageList property, which stores a reference to an ImageList control. Individual items in the control (like tree nodes or list rows) then use an ImageIndex or similar property, which identifies a single picture in the ImageList by index number (starting at 0). You look at examples that use this technique later in this chapter.

In the meantime, you should also note that the ImageList can be a useful way to store images that you need to use in any scenario. The example that follows loops through an ImageList and draws its images directly onto the surface of a form. The result is shown in Figure 6-2.

Figure 6-2: Directly outputting an ImageList

// Get the graphics device context for the form. Graphics g = this.CreateGraphics(); // Draw each image using the ImageList.Draw() method. for (int i = 0; i < iconImages.Images.Count; i++) { iconImages.Draw(g, 30 + i * 30, 30, i); } // Release the graphics device context. g.Dispose();